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Study on energy-saving design and operation of hospital purification air conditioning system

Study on energy-saving design and operation of hospital purification air conditioning system In order to ensure the cleanliness of operating room, clean air conditioners are installed in the clean operation departments in hospitals in China. Purification air conditioning system is an air conditioning system with a special function that ensures the cleanliness of the operating room and the required tem- perature and humidity in the operating room to avoid infection. This paper took the energy-saving design of the clean air-conditioning system of the clean operation department of the First Affiliated Hospital of Wenzhou Medical College, Zhejiang, China, as an example to illustrate the energy-saving methods such as layout optimization, air-conditioning division, secondary return air setting and oper- ation mode adjustment. The energy consumption of primary return air technology and secondary return air technology was calculated. The results showed that energy-saving design could save nearly one-third of energy, improve the level of air-conditioning operation and management, reduce costs, and improve resource utilization, which is of great significance to social development. Keywords: purification; air conditioning; surgery; energy-saving design Received 16 January 2018; revised 28 February 2018; editorial decision 19 March 2018; accepted 29 *Corresponding author: [email protected] March 2018 ......... ................. ................ ................. ................. ................ ................. ................. . ............... ................. ................. operating room of the hospital, the air conditioning system needs 1 INTRODUCTION to be properly maintained. As clean air conditioning system design The cleanliness of hospitals, especially the environmental cleanli- candirectlyaffect theair qualityand operatingenergyconsump- ness of the operating room [1, 2], is directly related to the health tion, air conditioning energy-saving design is particularly import- of patients and medical staffs. With the further development of ant. In the study of Tabata et al. [6], the combination of desiccant medical and health care in China, the level of surgery has been air conditioning system and the cold water large temperature dif- improved [3]. As a result, clean surgical department is born to ference water supply system achieved an energy saving of 41% a ensure that operating room environment meet national standards. year. On the basis of comparative analysis of indoor comfort para- Clean surgical department should use clean air technology and meters such as temperature and wind speed, Wang et al. [7]used establish scientific staff, logistics and zoning management to con- the improved radiation heat transfer method to solve the tempera- trol particulate pollution [4] and ensure the safety of surgical ture model of the inner surface of building envelope and calculated patients. Gniadek et al. mentioned in their work [5] that infection the theoretical load index. The flow field and parameters generated during surgery was a risk factor which intervened in treatment by computational fluid dynamics were used to effectively analyze and eradicating microorganisms in the operating room environ- the indoor thermal comfort in full air conditioning and stratified ment might help to reduce the incidence of infection, while laminar air conditioning design and the stratified air conditioning design air conditioners significantly reduced the number of microorgan- was recommended in large space buildings. Taking a Grade A hos- isms in hospital environment. By collecting and testing fungi in a pital in Wuhan as the research object, Li et al. [8]conducted an hospital’s air samples, they found 48 out of 50 air samples with audit on the hospital’s energy consumption system. After energy- fungal growths. Hence, in order to ensure the cleanliness of the saving reform on the lighting system and central heating and International Journal of Low-Carbon Technologies 2018, 13, 184–190 © The Author(s) 2018. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re- use, please contact [email protected] doi:10.1093/ijlct/cty013 Advance Access Publication 12 April 2018 184 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system energy control system, the final comprehensive reform energy- rooms should be set in the non-clean area, while the waiting area saving rate was 31.71%, saving 318.01tce (ton of standard coal and washroom should be set in the comfortable air-conditioned equivalent). The purpose of this study is to save energy and pro- area. Connecting the auxiliary room with the operating room can mote sustainable development through the energy-saving design of reduce the waste of time, speed up the surgical procedure and the clean air-conditioning system in the clean operation depart- improve the operation efficiency. Through setting the clean auxil- ment of a hospital. iary rooms, non-cleaning auxiliary rooms and other functional rooms in different regions, different design on air supply for the clean air-conditioning can be realized according to the cleanliness 2 OVERVIEW OF THE CLEAN OPERATION of different regions. The energy consumption of decontamination air conditioners is reduced by installing comfortable air conditioners DEPARTMENT in the air conditioning areas. The layout optimization of the surgi- The clean operation department of the First Affiliated Hospital cal department will not only make thesurgicalflow moresmoothly, of Wenzhou Medical College, Zhejiang, China, is located on the but also save air conditioning energy consumption [9]. third floor of the medical technology department, and the purifi- cation equipment room is located on the fourth floor, with an 3.2 Air conditioning division area of 11 420 m . Purification central air conditioner with four- The air conditioner of the I level operating room applies one- pipe system and independent cold and heat source is used. The driven-one mode while that of the III level operating room operation department consists of 43 operating rooms and related applies one-driven-two or one-driven-three mode; both of them functional rooms, including 6 I level operating rooms and 37 III apply the secondary air return system. Each operating room level operating rooms, and involves positive and negative pres- discharges air independently with fresh air delivered. As the sure switching department, outpatient department, endoscopy area outside the building needs to be chilled in the summer and department, orthopedics department and general surgery depart- heated in the winter while the area inside the building needs ment. In addition, the clean surgical department is also divided year-round cooling, the air-conditioning system is divided into into three regions, OR1–OR13 is region one, OR14–OR26 is the interior and exterior partitions reasonably to avoid the situ- region two, and OR27–OR43 is region three; each region is inde- ation that the cooling and heating offset each other [10]. pendently controlled. OR22–OR26 are emergency operating rooms and OR14–OR21 are night or emergency rooms 3.3 Frequency conversion technology (Table 1), which can be used separately. All operating rooms The purification air conditioning operating mode is set to working have a ceiling height of 3 m, and some operating room profiles of mode and non-working mode while the working mode is divided the clean operation department are shown in Figure 1. into two modes: the one on winter and summer and the one on transition seasons. The frequency conversion technology is used in 3 COMMON ENERGY SAVING MEASURES fresh air units and purification cycle units for performing variable frequency regulation on fresh air volume under different working 3.1 Layout optimization of the surgical department modes [11]. In non-working mode, the air-conditioner operates Apart from operating rooms, there are subsidiary rooms in the sur- according to the minimum air volume required, which ensures the gical department. Clean auxiliary rooms should be set in the clean cleanliness of the operating room and saves energy. In winter and area, connected with the clean operating room. Non-clean auxiliary summer mode, it operates at the fresh air volume required for Table 1. The overview of the clean operation department. Region No. of operation room Clean class Area of operation room (m ) Category of operation room Region 1 OR2 Grade III 54.1 Neurosurgery (cerebral surgery) OR4 Grade III 52.71 General thoracic OR8 Grade III 31.55 Urinary surgery OR11 Grade I 73.06 Neurosurgery (cerebral surgery) OR12 Grade I 54.53 Cardiac (in vitro) Region 2 OR14 Grade I 71.16 Hybrid (vascular surgery) OR16 Grade III 54.94 Orthopedics OR19 Grade III 52.71 General Surgery OR25 Grade III 27.18 Emergency treatment OR26 Grade III 30.74 Positive–negative pressure Region 3 OR32 Grade III 40.42 Tumor OR35 Grade III 46.8 Ear, nose, and throat OR36 Grade III 31.28 Burn surgery OR39 Grade III 34.92 Outpatient OR43 Grade III 27.76 Outpatient International Journal of Low-Carbon Technologies 2018, 13, 184–190 185 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Y. Chen Figure 1. Plan graph of the clean surgical department. normal operation. In transition season mode, it operates at the devices. Air filter has three stalls, namely, rough efficiency, effi- maximum required air volume, which effectively reduces energy ciency, high efficiency, which have different degrees of air treat- consumption and optimizes operation. ment. Air blowing function is realized through the circulation fan, which forms wind by air motion. Air temperature and humidity control is completed by the surface cooler and heating 3.4 Secondary return air system and humidification device. Different from the industrial clean Purifying air conditioning is different from comfort air condi- room, the purification air conditioning system in the clean tioning, its air output is large and supply air temperature differ- operating room often uses multi-machine centralized air- ence and heat load are small in the process of heat and conditioning system, installs all units in the air-conditioned humidity treatment. Though primary return air system is com- room, with the fresh air delivered through the air supply duct monly applied nowadays with its advantages of simple structure at the top of the operating room after filtered by the filter. and operation, its energy consumption is large due to the hot and cold offset phenomenon between its cooling and heating coils. In contrast, secondary return air system does not have 4.2 Cold heat source setting and fresh air supply this problem. Instead, by utilizing the return air temperature, way the system can greatly reduce equipment operating costs, save The cold and heat source setting of the clean operation depart- energy and promote sustainable energy development [12]. ment is determined based on the cold and heat source setting of the whole medical building. The central cooling (heating) mode and the independent decentralized cooling (heating) 4 AIR CONDITIONING ENERGY-SAVING source configuration mode are applied. When the central DESIGN source of cooling (heating) cannot fully meet the requirements of the air-conditioning system of the clean surgery department, 4.1 Purification air conditioning system analysis the independent decentralized cooling (heating) source can Purification air conditioning system consists of air filters, circu- meet the requirements of the operation department, making the lating fans, surface coolers and heating and humidification clean air conditioner flexible and economical, and can satisfy 186 International Journal of Low-Carbon Technologies 2018, 13, 184–190 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system the emergency use requirements of the operation department. However, its cooling adjustment range is limited, with poor temperature and humidity control performance, and it is diffi- cult to maintain the stability of temperature and humidity. Hence, the local centralized cooling (heating) and independent decentralized cooling (heating) source configuration mode can be used. This configuration can meet the requirements of sur- geries with high temperature and humidity stability require- ments, with good energy-saving performance [13]. Fresh air treatment is divided into fresh air dispersion treat- ment and fresh air concentration treatment. Fresh air disper- sion treatment refers to the treatment of fresh air after fresh air is mixed with the return air while fresh air concentration treat- ment refers to the treatment of fresh air before fresh air is mixed with the return air. In this design, fresh air concentration treatment is preferred since it can ensure the simple mainten- ance of the air conditioning system, save management costs and avoid the change of microbiological equilibrium when return air meets the unprocessed fresh air. 4.3 Various types of clean room parameter indexes Before the design of air conditioning system of clean operation department [14], we need to understand the requirements of air conditioning system design. Although the accuracy requirement of the clean operating room for indoor temperature and humid- ity is not high, it is necessary to ensure that the bacterial con- centration is controlled within a certain range under such conditions of temperature and humidity [15]. Besides, different levels of clean operating room have different requirements on the times of ventilation. There are two levels of clean surgical room in the clean operation department of the First Affiliated Hospital of Wenzhou Medical College, i.e. I level and III level. As shown in Table 2, the I level surgical room requires 0.2 bacteria in the surgical area/30 min · φ90 vessel (5 bacteria/m ) and 0.4 bac- teria in the surrounding area/30 min · φ90 vessel (10 bacteria/ m ), while the III level surgical room requires 2 bacteria in the surgical area/30 min · φ90 vessel (75 bacteria/m ) and 4 bacteria in the surrounding area/30 min · φ90 vessel (150 bacteria/m ). In addition, the I level surgical room requires the working face height interface average wind speed to be 0.25–0.30 m/s, the temperature to be between 22°C and 25°C, and the relative humidity to be between 40% and 60% RH, while the III level surgical room requires the times of ventilation to be 20–24 times/h, temperature between 22°C and 25°C, and relative humidity between 35% and 60% RH. 4.4 Determination of design parameters Cooling load refers to the heat, including both sensible heat and latent heat, taken away from the room by the air condition- ing system in order to keep the indoor hot and humid environ- ment and temperature at a specified level. As the clean surgical department does not have doors or windows that have direct contact with the outside world, the solar radiation heat and International Journal of Low-Carbon Technologies 2018, 13, 184–190 187 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Table 2. Clean room level parameters in the clean surgical department. Level of the operating room The maximum average concentration of bacteria of sedimentation Air cleanliness class Ventilation Working surface height Temperature Relative (phytoplankton) in the operation area times (times/h) interface average wind (°C) humidity speed (m/s) (% RH) I level Clean operating room 0.2 bacteria in the surgical area/30 min · φ90 vessel (5 bacteria/ Surgical area: 100 level / 0.25–0.30 22–25 40–60 m ) Surrounding area: 1000 level 0.4 bacteria in the surrounding area/30 min · φ90 vessel (10 bacteria /m ) Clean auxiliary room 0.2 bacteria in the local area/30 min · φ90 vessel (5 bacteria /m ) 1000 level (local 100 level) / / / / 0.4 bacteria in the surrounding area/30 min · φ90 vessel (10 bacteria/m ) III Clean operating room 2 bacteria in the surgical area/30 min · φ90 vessel (75 bacteria/m ) Surgical area: 10 000 level 20–24 / 22–25 35–60 level 4 bacteria in the surrounding area/30 min · φ90 vessel (150 Surrounding area: 100 000 level bacteria/m ) Clean auxiliary room 4 bacteria/30 min · φ90 vessel (150 bacteria/m ) 100 000 level / / / / Y. Chen Table 3. Human body load calculation results. Level of the Extreme light physical labor Light physical labor Humidity Cooling operating load (g/h) load (W) Number Individual Individual Individual Number Individual Individual Individual room of people sensible heat latent heat moisture gain of people sensible heat latent heat moisture gain (W) (W) (g/h) (W) (W) (g/h) I level 2 70 64 96 10 70 112 167 1862 2088 III level 2 70 64 96 8 70 112 167 1528 1724 Table 4. Heat and wet load in the clean operating room. Level of the Indoor design Body cooling Body humidity Equipment cooling Lighting cooling Total cooling Heat and moisture operating room temperature (°C) load (w) load (kg/h) load (w) load (w) load (w) ratio (kJ/kg) I level (45 m ) 24 2088 1.862 3320 420 5828 11 268 III level (35 m ) 24 1724 1.528 3320 420 5464 12 873 heat brought through air infiltration can be ignored. Human The cooling load of the equipment is: body heat dissipation, lighting heat dissipation and equipment C = c CCle, ee heat dissipation are considered, that is, human body cooling load, lighting cooling load and equipment cooling load. In the where C refers to cooling load of equipment heat dissipation actual calculation, the cluster coefficient which is calculated (W), C refers to the heat dissipation amount of equipment according to the age, gender, and intensity of members based (W), and CCle refers to the cooling load coefficient of equip- on the heat and wet dissipation capacity of an adult man ment heat dissipation. needed to be taken into consideration. The heat and wet dissi- Based on the power of common equipment and lamps in the pation capacity of an adult woman is 85% that of an adult men, operating room, the cooling load of the equipment was 3320 W while that of a child is 75% that of an adult man; therefore clus- and the cooling load of the lighting was 420 W. Table 4 shows ter coefficient = (number of adult men + number of adult the total indoor load of the clean operating room under steady- women ∗ 85% + number of children ∗ 75%)/total number of state conditions. people. Total body cooling load in the operating room was: C =′ cnn , rr 4.5 Analysis on the primary and secondary return where C refers to body heat dissipation cooling load (W), C air system r r refers to body total heat load (W), n refers to the total number As mentioned before, the primary return air system had severe of people, and n′ refers to the cluster coefficient. hot and cold offset phenomenon and large energy consumption The total body wet load in the operating room was: while the secondary return air system could greatly reduce equipment operating costs and save energy consumption. In H=′ hnn , ss this section, the cooling load and energy consumption of the two systems were analyzed. In summer, outdoor design para- where H refers to body wet dissipation humid load (kg/h), h s s meters are as follows: 35°C of dry bulb temperature, 28°Cof refers to body wet dissipation amount (g/h), n refers to the total wet bulb temperature; indoor design parameters were as fol- number of people, and n′ refers to the cluster coefficient. lows: 24°C of room temperature and 50% of relative humidity. According to the parameters in Table 2, the room tempera- Based on the cross section wind speed and ventilation time ture was set at a constant temperature of 24°C, and the relative requirements of the operating room in Table 2, the amount of humidity was set as 50%. There were 12 people in III level sur- air supply of the air-conditioning system was determined. The gical room and 10 people in III level surgical room. Two people local air – ventilation system was used. In the I level surgical were of extreme light physical labor and others were of light room, the fresh air volume was 1000 m /h, the return air vol- physical labor, the results are shown in Table 3. 3 3 ume was 9000 m /h, the exhaust air volume was 555 m /h, and Lighting cooling load was: the amount of air supply was 10 000 m /h; in the III level surgi- cal room, the fresh air volume was 800 m /h, the return air vol- C = c CClz, zz 3 3 ume was 1100 m /h, the exhaust air volume was 560 m /h, and where C refers to lighting heat dissipation cooling load (W), C the air supply volume was 1900 m /h. z z refers to lighting heat dissipation amount (W), and CCl refers Hence, it was calculated out that the air enthalpy difference to cooling load coefficient of lighting heat dissipation. and the machine dew point enthalpy was 0.912 kJ/kg and 188 International Journal of Low-Carbon Technologies 2018, 13, 184–190 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system Table 5. Cooling load of the primary return airy system. Level of the operating room Fresh air Heat humidity Indoor Fresh air Reheat Fan temperature rise Cooling volume (m /h) ratio (kJ/kg) load (kW) load (kW) load (kW) load load (kW) Fresh Air air (kW) supply (kW) Primary return air system I level 1000 11 268 5.828 15.96 36.06 0.53 5.78 64.158 III level 800 12 873 5.464 12.44 11.12 0.41 1.94 31.374 Secondary return air system I level 1000 11 268 5.828 11.86 / 0.53 5.78 23.998 III level 800 12 873 5.464 11.42 / 0.41 1.94 19.234 Figure 2. Cooling load in the clean operating room. 2.374 kJ/kg, 35.11 kJ/kg and 35.06 kJ/kg, respectively in the I As shown in Figure 2, on the cooling load of the primary level surgical room and the III level surgical room. As the pri- return air system, whether it was level I operating room or level mary return air system had a reheat process, its cooling load III operating room, the proportion of reheat load was the lar- was composed of the indoor load, fresh air load, reheat load gest. The reheat load accounted for 56.20% of the total cooling and fan temperature rise load while the secondary return air load in level I operating room and 35.44% in level III operating system had no reheat load, as shown in Table 5. room. Without reheat load, the secondary return air system Figure 2 is obtained after calculating the proportion of each saved most of the energy consumption. load in the total cooling. As shown in Table 5, the cooling load of primary return air system in operation room I was 64.158 kW, that of secondary 5 CONCLUSIONS return air system was 23.998 kW, saving 167.35%. The cooling load of primary return air system in III level operating room In addition to ensure that the indoor temperature and humidity was 31.374 kW, that of the secondary air return system was and differential pressure are within the standard range, the 19.234 kW, saving 63.12%. clean air conditioner in the clean surgery department also needs International Journal of Low-Carbon Technologies 2018, 13, 184–190 189 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Y. Chen [4] Barbadoro P, Bruschi R, Martini E, et al. Impact of laminar air flow on to ensure that the indoor air concentration of bacteria and dust operating room contamination, and surgical wound infection rates in clean particles are within the standard range in order to reduce the and contaminated surgery. Eur J Surg Oncol 2016;42:1756–8. risk of wound infection in patients and ensure the health of [5] Gniadek A, Macura AB. Air-conditioning vs. presence of pathogenic fungi health care workers. Therefore, the operating effect of clean air in hospital operating theatre environment. Wiad Parazytol 2011;57:103–6. conditioning is extremely important. While ensuring the effect- [6] Tabata Y, Sugihara Y, Muramatsu H. D-67 verification of the energy- iveness of clean air conditioning, we should also consider the saving effect by the desiccant air-conditioning system of the hospital in energy-saving aspect. In this paper, energy-saving methods Okinawa. Biophys J 2015;108:128a. were explored and designed to determine the relevant para- [7] Wang Y, Wong KKL, Du HM, et al. Design configuration for a higher effi- meters of the purification air-conditioning system and the con- ciency air conditioning system in large space building. Energy Build 2014; figuration of cold and heat sources and fresh air supply ways. 72:167–76. [8] Li YY, Zhang Z, Li HC, et al. The analysis on energy saving reconstruction Besides, the energy consumption of primary and secondary of a Grade III-A General Hospital in Wuhan. Adv Mater Res 2012;594-597: return air system was compared and the results showed that the 2077–81. cooling capacity of the secondary return air system reduced [9] Elhelw M. Analysis of energy management for heating, ventilating and air- most of the energy consumption compared to the primary conditioning systems. Alex Eng J 2016;55:811–8. return air system, the I level surgical room saved energy by [10] Yaşa E, Ok V. Evaluation of the effects of courtyard building shapes on 167.35% and the III level surgical room saved energy by solar heat gains and energy efficiency according to different climatic 560.20%. Therefore, secondary return air was more energy effi- regions. Energy Build 2014;73:192–9. cient than primary return air. The energy-saving design of the [11] Meng QL, Yan XY, Ren QC. Global optimal control of variable air volume clean air-conditioning system is of great significance to sustain- air-conditioning system with iterative learning: an experimental case study. able development and deserves further discussion. J Zhejiang Universityence A 2015;16:302–15. [12] Omer AM. Energy and environment: applications and sustainable develop- ment. Br J Environ Clim Change 2011;1:118–58. REFERENCES [13] Zhang G, Xiong J, Gao H, et al. Hospital operating room clean air- conditioning system: design and application. J Environ Health 2010;27: [1] Wahr JA, Abernathy JH. Environmental hygiene in the operating room: 814–7. cleanliness, godliness, and reality. Int Anesthesiol Clin 2013;51:93–104. [14] Wang Q, Meng QL. A new energy-saving air handling unit for clean oper- [2] Lecordier J, Plivard C, Gardeux M, et al. To create a cleanroom controlled ating room. International conference on digital manufacturing and auto- environment using a mobile air decontamination unit for the preparation mation. IEEE 2011;1:58–62. of antineoplastic drugs. J Oncol Pharm Pract 2016;22:151. [15] Fen X, Xu ZL. Necessity of particulate pollutant control in clean operating [3] Itani M, Iwayama S, Shigeta E, et al. Perioperative infection and mainten- environment: Part 2 of the series of research practice of the revision task ance of the operating room environment. J Japan Soc Clin Anesth 2015;35: group of the Architectural technical code for hospital clean operating 061–6. department. Heat Ventilating Airconditioning 2013;43:1–5. 190 International Journal of Low-Carbon Technologies 2018, 13, 184–190 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png International Journal of Low-Carbon Technologies Oxford University Press

Study on energy-saving design and operation of hospital purification air conditioning system

Chen, Yunyu
International Journal of Low-Carbon Technologies , Volume Advance Article (2) – Apr 12, 2018
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Oxford University Press
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© The Author(s) 2018. Published by Oxford University Press.
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10.1093/ijlct/cty013
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Abstract

In order to ensure the cleanliness of operating room, clean air conditioners are installed in the clean operation departments in hospitals in China. Purification air conditioning system is an air conditioning system with a special function that ensures the cleanliness of the operating room and the required tem- perature and humidity in the operating room to avoid infection. This paper took the energy-saving design of the clean air-conditioning system of the clean operation department of the First Affiliated Hospital of Wenzhou Medical College, Zhejiang, China, as an example to illustrate the energy-saving methods such as layout optimization, air-conditioning division, secondary return air setting and oper- ation mode adjustment. The energy consumption of primary return air technology and secondary return air technology was calculated. The results showed that energy-saving design could save nearly one-third of energy, improve the level of air-conditioning operation and management, reduce costs, and improve resource utilization, which is of great significance to social development. Keywords: purification; air conditioning; surgery; energy-saving design Received 16 January 2018; revised 28 February 2018; editorial decision 19 March 2018; accepted 29 *Corresponding author: [email protected] March 2018 ......... ................. ................ ................. ................. ................ ................. ................. . ............... ................. ................. operating room of the hospital, the air conditioning system needs 1 INTRODUCTION to be properly maintained. As clean air conditioning system design The cleanliness of hospitals, especially the environmental cleanli- candirectlyaffect theair qualityand operatingenergyconsump- ness of the operating room [1, 2], is directly related to the health tion, air conditioning energy-saving design is particularly import- of patients and medical staffs. With the further development of ant. In the study of Tabata et al. [6], the combination of desiccant medical and health care in China, the level of surgery has been air conditioning system and the cold water large temperature dif- improved [3]. As a result, clean surgical department is born to ference water supply system achieved an energy saving of 41% a ensure that operating room environment meet national standards. year. On the basis of comparative analysis of indoor comfort para- Clean surgical department should use clean air technology and meters such as temperature and wind speed, Wang et al. [7]used establish scientific staff, logistics and zoning management to con- the improved radiation heat transfer method to solve the tempera- trol particulate pollution [4] and ensure the safety of surgical ture model of the inner surface of building envelope and calculated patients. Gniadek et al. mentioned in their work [5] that infection the theoretical load index. The flow field and parameters generated during surgery was a risk factor which intervened in treatment by computational fluid dynamics were used to effectively analyze and eradicating microorganisms in the operating room environ- the indoor thermal comfort in full air conditioning and stratified ment might help to reduce the incidence of infection, while laminar air conditioning design and the stratified air conditioning design air conditioners significantly reduced the number of microorgan- was recommended in large space buildings. Taking a Grade A hos- isms in hospital environment. By collecting and testing fungi in a pital in Wuhan as the research object, Li et al. [8]conducted an hospital’s air samples, they found 48 out of 50 air samples with audit on the hospital’s energy consumption system. After energy- fungal growths. Hence, in order to ensure the cleanliness of the saving reform on the lighting system and central heating and International Journal of Low-Carbon Technologies 2018, 13, 184–190 © The Author(s) 2018. Published by Oxford University Press. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re- use, please contact [email protected] doi:10.1093/ijlct/cty013 Advance Access Publication 12 April 2018 184 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system energy control system, the final comprehensive reform energy- rooms should be set in the non-clean area, while the waiting area saving rate was 31.71%, saving 318.01tce (ton of standard coal and washroom should be set in the comfortable air-conditioned equivalent). The purpose of this study is to save energy and pro- area. Connecting the auxiliary room with the operating room can mote sustainable development through the energy-saving design of reduce the waste of time, speed up the surgical procedure and the clean air-conditioning system in the clean operation depart- improve the operation efficiency. Through setting the clean auxil- ment of a hospital. iary rooms, non-cleaning auxiliary rooms and other functional rooms in different regions, different design on air supply for the clean air-conditioning can be realized according to the cleanliness 2 OVERVIEW OF THE CLEAN OPERATION of different regions. The energy consumption of decontamination air conditioners is reduced by installing comfortable air conditioners DEPARTMENT in the air conditioning areas. The layout optimization of the surgi- The clean operation department of the First Affiliated Hospital cal department will not only make thesurgicalflow moresmoothly, of Wenzhou Medical College, Zhejiang, China, is located on the but also save air conditioning energy consumption [9]. third floor of the medical technology department, and the purifi- cation equipment room is located on the fourth floor, with an 3.2 Air conditioning division area of 11 420 m . Purification central air conditioner with four- The air conditioner of the I level operating room applies one- pipe system and independent cold and heat source is used. The driven-one mode while that of the III level operating room operation department consists of 43 operating rooms and related applies one-driven-two or one-driven-three mode; both of them functional rooms, including 6 I level operating rooms and 37 III apply the secondary air return system. Each operating room level operating rooms, and involves positive and negative pres- discharges air independently with fresh air delivered. As the sure switching department, outpatient department, endoscopy area outside the building needs to be chilled in the summer and department, orthopedics department and general surgery depart- heated in the winter while the area inside the building needs ment. In addition, the clean surgical department is also divided year-round cooling, the air-conditioning system is divided into into three regions, OR1–OR13 is region one, OR14–OR26 is the interior and exterior partitions reasonably to avoid the situ- region two, and OR27–OR43 is region three; each region is inde- ation that the cooling and heating offset each other [10]. pendently controlled. OR22–OR26 are emergency operating rooms and OR14–OR21 are night or emergency rooms 3.3 Frequency conversion technology (Table 1), which can be used separately. All operating rooms The purification air conditioning operating mode is set to working have a ceiling height of 3 m, and some operating room profiles of mode and non-working mode while the working mode is divided the clean operation department are shown in Figure 1. into two modes: the one on winter and summer and the one on transition seasons. The frequency conversion technology is used in 3 COMMON ENERGY SAVING MEASURES fresh air units and purification cycle units for performing variable frequency regulation on fresh air volume under different working 3.1 Layout optimization of the surgical department modes [11]. In non-working mode, the air-conditioner operates Apart from operating rooms, there are subsidiary rooms in the sur- according to the minimum air volume required, which ensures the gical department. Clean auxiliary rooms should be set in the clean cleanliness of the operating room and saves energy. In winter and area, connected with the clean operating room. Non-clean auxiliary summer mode, it operates at the fresh air volume required for Table 1. The overview of the clean operation department. Region No. of operation room Clean class Area of operation room (m ) Category of operation room Region 1 OR2 Grade III 54.1 Neurosurgery (cerebral surgery) OR4 Grade III 52.71 General thoracic OR8 Grade III 31.55 Urinary surgery OR11 Grade I 73.06 Neurosurgery (cerebral surgery) OR12 Grade I 54.53 Cardiac (in vitro) Region 2 OR14 Grade I 71.16 Hybrid (vascular surgery) OR16 Grade III 54.94 Orthopedics OR19 Grade III 52.71 General Surgery OR25 Grade III 27.18 Emergency treatment OR26 Grade III 30.74 Positive–negative pressure Region 3 OR32 Grade III 40.42 Tumor OR35 Grade III 46.8 Ear, nose, and throat OR36 Grade III 31.28 Burn surgery OR39 Grade III 34.92 Outpatient OR43 Grade III 27.76 Outpatient International Journal of Low-Carbon Technologies 2018, 13, 184–190 185 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Y. Chen Figure 1. Plan graph of the clean surgical department. normal operation. In transition season mode, it operates at the devices. Air filter has three stalls, namely, rough efficiency, effi- maximum required air volume, which effectively reduces energy ciency, high efficiency, which have different degrees of air treat- consumption and optimizes operation. ment. Air blowing function is realized through the circulation fan, which forms wind by air motion. Air temperature and humidity control is completed by the surface cooler and heating 3.4 Secondary return air system and humidification device. Different from the industrial clean Purifying air conditioning is different from comfort air condi- room, the purification air conditioning system in the clean tioning, its air output is large and supply air temperature differ- operating room often uses multi-machine centralized air- ence and heat load are small in the process of heat and conditioning system, installs all units in the air-conditioned humidity treatment. Though primary return air system is com- room, with the fresh air delivered through the air supply duct monly applied nowadays with its advantages of simple structure at the top of the operating room after filtered by the filter. and operation, its energy consumption is large due to the hot and cold offset phenomenon between its cooling and heating coils. In contrast, secondary return air system does not have 4.2 Cold heat source setting and fresh air supply this problem. Instead, by utilizing the return air temperature, way the system can greatly reduce equipment operating costs, save The cold and heat source setting of the clean operation depart- energy and promote sustainable energy development [12]. ment is determined based on the cold and heat source setting of the whole medical building. The central cooling (heating) mode and the independent decentralized cooling (heating) 4 AIR CONDITIONING ENERGY-SAVING source configuration mode are applied. When the central DESIGN source of cooling (heating) cannot fully meet the requirements of the air-conditioning system of the clean surgery department, 4.1 Purification air conditioning system analysis the independent decentralized cooling (heating) source can Purification air conditioning system consists of air filters, circu- meet the requirements of the operation department, making the lating fans, surface coolers and heating and humidification clean air conditioner flexible and economical, and can satisfy 186 International Journal of Low-Carbon Technologies 2018, 13, 184–190 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system the emergency use requirements of the operation department. However, its cooling adjustment range is limited, with poor temperature and humidity control performance, and it is diffi- cult to maintain the stability of temperature and humidity. Hence, the local centralized cooling (heating) and independent decentralized cooling (heating) source configuration mode can be used. This configuration can meet the requirements of sur- geries with high temperature and humidity stability require- ments, with good energy-saving performance [13]. Fresh air treatment is divided into fresh air dispersion treat- ment and fresh air concentration treatment. Fresh air disper- sion treatment refers to the treatment of fresh air after fresh air is mixed with the return air while fresh air concentration treat- ment refers to the treatment of fresh air before fresh air is mixed with the return air. In this design, fresh air concentration treatment is preferred since it can ensure the simple mainten- ance of the air conditioning system, save management costs and avoid the change of microbiological equilibrium when return air meets the unprocessed fresh air. 4.3 Various types of clean room parameter indexes Before the design of air conditioning system of clean operation department [14], we need to understand the requirements of air conditioning system design. Although the accuracy requirement of the clean operating room for indoor temperature and humid- ity is not high, it is necessary to ensure that the bacterial con- centration is controlled within a certain range under such conditions of temperature and humidity [15]. Besides, different levels of clean operating room have different requirements on the times of ventilation. There are two levels of clean surgical room in the clean operation department of the First Affiliated Hospital of Wenzhou Medical College, i.e. I level and III level. As shown in Table 2, the I level surgical room requires 0.2 bacteria in the surgical area/30 min · φ90 vessel (5 bacteria/m ) and 0.4 bac- teria in the surrounding area/30 min · φ90 vessel (10 bacteria/ m ), while the III level surgical room requires 2 bacteria in the surgical area/30 min · φ90 vessel (75 bacteria/m ) and 4 bacteria in the surrounding area/30 min · φ90 vessel (150 bacteria/m ). In addition, the I level surgical room requires the working face height interface average wind speed to be 0.25–0.30 m/s, the temperature to be between 22°C and 25°C, and the relative humidity to be between 40% and 60% RH, while the III level surgical room requires the times of ventilation to be 20–24 times/h, temperature between 22°C and 25°C, and relative humidity between 35% and 60% RH. 4.4 Determination of design parameters Cooling load refers to the heat, including both sensible heat and latent heat, taken away from the room by the air condition- ing system in order to keep the indoor hot and humid environ- ment and temperature at a specified level. As the clean surgical department does not have doors or windows that have direct contact with the outside world, the solar radiation heat and International Journal of Low-Carbon Technologies 2018, 13, 184–190 187 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Table 2. Clean room level parameters in the clean surgical department. Level of the operating room The maximum average concentration of bacteria of sedimentation Air cleanliness class Ventilation Working surface height Temperature Relative (phytoplankton) in the operation area times (times/h) interface average wind (°C) humidity speed (m/s) (% RH) I level Clean operating room 0.2 bacteria in the surgical area/30 min · φ90 vessel (5 bacteria/ Surgical area: 100 level / 0.25–0.30 22–25 40–60 m ) Surrounding area: 1000 level 0.4 bacteria in the surrounding area/30 min · φ90 vessel (10 bacteria /m ) Clean auxiliary room 0.2 bacteria in the local area/30 min · φ90 vessel (5 bacteria /m ) 1000 level (local 100 level) / / / / 0.4 bacteria in the surrounding area/30 min · φ90 vessel (10 bacteria/m ) III Clean operating room 2 bacteria in the surgical area/30 min · φ90 vessel (75 bacteria/m ) Surgical area: 10 000 level 20–24 / 22–25 35–60 level 4 bacteria in the surrounding area/30 min · φ90 vessel (150 Surrounding area: 100 000 level bacteria/m ) Clean auxiliary room 4 bacteria/30 min · φ90 vessel (150 bacteria/m ) 100 000 level / / / / Y. Chen Table 3. Human body load calculation results. Level of the Extreme light physical labor Light physical labor Humidity Cooling operating load (g/h) load (W) Number Individual Individual Individual Number Individual Individual Individual room of people sensible heat latent heat moisture gain of people sensible heat latent heat moisture gain (W) (W) (g/h) (W) (W) (g/h) I level 2 70 64 96 10 70 112 167 1862 2088 III level 2 70 64 96 8 70 112 167 1528 1724 Table 4. Heat and wet load in the clean operating room. Level of the Indoor design Body cooling Body humidity Equipment cooling Lighting cooling Total cooling Heat and moisture operating room temperature (°C) load (w) load (kg/h) load (w) load (w) load (w) ratio (kJ/kg) I level (45 m ) 24 2088 1.862 3320 420 5828 11 268 III level (35 m ) 24 1724 1.528 3320 420 5464 12 873 heat brought through air infiltration can be ignored. Human The cooling load of the equipment is: body heat dissipation, lighting heat dissipation and equipment C = c CCle, ee heat dissipation are considered, that is, human body cooling load, lighting cooling load and equipment cooling load. In the where C refers to cooling load of equipment heat dissipation actual calculation, the cluster coefficient which is calculated (W), C refers to the heat dissipation amount of equipment according to the age, gender, and intensity of members based (W), and CCle refers to the cooling load coefficient of equip- on the heat and wet dissipation capacity of an adult man ment heat dissipation. needed to be taken into consideration. The heat and wet dissi- Based on the power of common equipment and lamps in the pation capacity of an adult woman is 85% that of an adult men, operating room, the cooling load of the equipment was 3320 W while that of a child is 75% that of an adult man; therefore clus- and the cooling load of the lighting was 420 W. Table 4 shows ter coefficient = (number of adult men + number of adult the total indoor load of the clean operating room under steady- women ∗ 85% + number of children ∗ 75%)/total number of state conditions. people. Total body cooling load in the operating room was: C =′ cnn , rr 4.5 Analysis on the primary and secondary return where C refers to body heat dissipation cooling load (W), C air system r r refers to body total heat load (W), n refers to the total number As mentioned before, the primary return air system had severe of people, and n′ refers to the cluster coefficient. hot and cold offset phenomenon and large energy consumption The total body wet load in the operating room was: while the secondary return air system could greatly reduce equipment operating costs and save energy consumption. In H=′ hnn , ss this section, the cooling load and energy consumption of the two systems were analyzed. In summer, outdoor design para- where H refers to body wet dissipation humid load (kg/h), h s s meters are as follows: 35°C of dry bulb temperature, 28°Cof refers to body wet dissipation amount (g/h), n refers to the total wet bulb temperature; indoor design parameters were as fol- number of people, and n′ refers to the cluster coefficient. lows: 24°C of room temperature and 50% of relative humidity. According to the parameters in Table 2, the room tempera- Based on the cross section wind speed and ventilation time ture was set at a constant temperature of 24°C, and the relative requirements of the operating room in Table 2, the amount of humidity was set as 50%. There were 12 people in III level sur- air supply of the air-conditioning system was determined. The gical room and 10 people in III level surgical room. Two people local air – ventilation system was used. In the I level surgical were of extreme light physical labor and others were of light room, the fresh air volume was 1000 m /h, the return air vol- physical labor, the results are shown in Table 3. 3 3 ume was 9000 m /h, the exhaust air volume was 555 m /h, and Lighting cooling load was: the amount of air supply was 10 000 m /h; in the III level surgi- cal room, the fresh air volume was 800 m /h, the return air vol- C = c CClz, zz 3 3 ume was 1100 m /h, the exhaust air volume was 560 m /h, and where C refers to lighting heat dissipation cooling load (W), C the air supply volume was 1900 m /h. z z refers to lighting heat dissipation amount (W), and CCl refers Hence, it was calculated out that the air enthalpy difference to cooling load coefficient of lighting heat dissipation. and the machine dew point enthalpy was 0.912 kJ/kg and 188 International Journal of Low-Carbon Technologies 2018, 13, 184–190 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Study on energy-saving design and operation of hospital purification air conditioning system Table 5. Cooling load of the primary return airy system. Level of the operating room Fresh air Heat humidity Indoor Fresh air Reheat Fan temperature rise Cooling volume (m /h) ratio (kJ/kg) load (kW) load (kW) load (kW) load load (kW) Fresh Air air (kW) supply (kW) Primary return air system I level 1000 11 268 5.828 15.96 36.06 0.53 5.78 64.158 III level 800 12 873 5.464 12.44 11.12 0.41 1.94 31.374 Secondary return air system I level 1000 11 268 5.828 11.86 / 0.53 5.78 23.998 III level 800 12 873 5.464 11.42 / 0.41 1.94 19.234 Figure 2. Cooling load in the clean operating room. 2.374 kJ/kg, 35.11 kJ/kg and 35.06 kJ/kg, respectively in the I As shown in Figure 2, on the cooling load of the primary level surgical room and the III level surgical room. As the pri- return air system, whether it was level I operating room or level mary return air system had a reheat process, its cooling load III operating room, the proportion of reheat load was the lar- was composed of the indoor load, fresh air load, reheat load gest. The reheat load accounted for 56.20% of the total cooling and fan temperature rise load while the secondary return air load in level I operating room and 35.44% in level III operating system had no reheat load, as shown in Table 5. room. Without reheat load, the secondary return air system Figure 2 is obtained after calculating the proportion of each saved most of the energy consumption. load in the total cooling. As shown in Table 5, the cooling load of primary return air system in operation room I was 64.158 kW, that of secondary 5 CONCLUSIONS return air system was 23.998 kW, saving 167.35%. The cooling load of primary return air system in III level operating room In addition to ensure that the indoor temperature and humidity was 31.374 kW, that of the secondary air return system was and differential pressure are within the standard range, the 19.234 kW, saving 63.12%. clean air conditioner in the clean surgery department also needs International Journal of Low-Carbon Technologies 2018, 13, 184–190 189 Downloaded from https://academic.oup.com/ijlct/article-abstract/13/2/184/4969362 by Ed 'DeepDyve' Gillespie user on 21 June 2018 Y. Chen [4] Barbadoro P, Bruschi R, Martini E, et al. Impact of laminar air flow on to ensure that the indoor air concentration of bacteria and dust operating room contamination, and surgical wound infection rates in clean particles are within the standard range in order to reduce the and contaminated surgery. Eur J Surg Oncol 2016;42:1756–8. risk of wound infection in patients and ensure the health of [5] Gniadek A, Macura AB. 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Journal

International Journal of Low-Carbon Technologies – Oxford University Press

Published: Apr 12, 2018

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