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1、Review of research on air-conditioning systems and indoor air quality control for human healthB.F.Yua,*, Z.B.Hua, M.Liua, H.L.Yangb, Q.X.Kongb, Y.H.LiubaSchool of Energy and Power Engineering, Xian Jiaotong University,28 Xian ning West Road, Xian, Shaanxi 710049,China bSchool of Human Settlement and
2、 Civil Engineering, Xian Jiao tong University,28 Xianning West Road, Xian, Shaanxi 710049,China3.Air-conditioning systems3.1.Air-conditioning systemsMany kinds of AC systems are used to improve indoor thermal comfort and IAQ. Recent research is focused on dedicated outdoor air system (DOAS),independ
3、ent control of temperature and humidity system(ICTHS),and cooling ceiling and displacement ventilation systems(CC/DV).3.1.1. Dedicated outdoor air system(DOAS)With the occurrence of SARS, avian flu and anthracnose in some countries, the safety of AC systems becomes more important. DOAS, an effective
4、 measure to realize immune building, has gradually been appreciated by international AC industry(Mumma,2001).The reason why DOAS is called ”new concept AC system is that the techniques used in DOAS have widely been applied but are subtly combined to show its broad prospect. DOAS results in a signifi
5、cant revolution in air-conditioning industry. Typical DOAS, shown in Fig.1,consists of the following several parts(Yin and Mumma,2003): Cold source: As the outlet air temperature of the outdoor air producer is required to be no more than 7 , its inlet water temperature should be no more than 4 . Tho
6、ugh the conventional chiller could be used as the cold source of DOAS, the out-let water temperature of the chiller should be no more than 5 C. So the chiller should be redesigned. The optimal cold source will be the ice-storage system.Outdoor air processor: To ensure that indoor terminal de-vices r
7、un in dry condition, outdoor air heat load, total latent heat load and partial sensible heat load are removed by am of typical DOAS. and to enhance the compatibility among different parts of DOAS.3.1.2. Independent control of temperature and humidity system(ICTHS) Conventional AC systems firstly coo
8、l air below the dew-point temperature in order to condense moisture out, and then reheat it to the supply comfortable temperature before delivering it to the occupied spaces. This leads to low evaporating temperature, a poor COP value for the chiller, and higher energy consumption. Moreover , the FC
9、U may become the hot-bed of many kinds of mildew due to the existence of condensing water, which will deteriorate IAQ. The reason for all these problems is that the cooling process and the dehumidifying process are in the same unit and at the same time, but there is an essential difference between t
10、he two processes( Chenet al.,2004).ICTHS can realize the independent control of temperature and humidity, and resolve the problems above.An ICTHS is shown in Fig.2 (Liu et al.,2006).The ICTHS consists of a liquid desiccant system and a cooling/heating grid system. The liquid desiccant system is comp
11、osed of out-door air processors (serving as dehumidifier in summer and humidifier in winter),a regenerator, and a desiccant storage tank. LiBr solution is used as liquid desiccant in the system, and the regeneration temperature is about 60 . The cooling/heating grid system is composed of the power d
12、riven refrigerator, the heat grid, and the FCU or radiant ceiling. In summer operations, valves A and C are turned on and valve B is turned off, and the ICTHS performs dehumidification and cooling of the air. Chilled water with temperature of 1518 flows from the refrigerator into the outdoor air pro
13、cessors and the indoor terminal devices. The outdoor air processors remove the total latent load and a portion of sensible load of the occupied space, while the indoor terminal devices deal with the remained sensible load.IAQ is greatly improved because of the following two main reasons:(i) indoor t
14、erminal devices operate in dry condition, and no condensing water will be produced on the surfaces of the AC system;(ii)the liquid desiccant can remove a number of pollutants from the air stream. In winter operations, valves A and C are turned off and valve B is turned on, and the ICTHS performs hum
15、idification and heating of the air. Hot water from the heat grid flows into the outdoor air processors and indoor terminal devices. The operating principle of the out-door air processor is shown in Fig.3.The outdoor air processor consists of two parts. The left of the broken line is a three- stage t
16、otal heat recovery device using liquid desiccant, and the right of the broken line is a single-stage spray unit (Li et al., 2003).The ICTHS can not only improve IAQ but reduce energy consumption and operation cost. In summer, when the latent load of the building covers from 10%to 50%, the primary energy consumption of the ICTHS is 7680%and the operation cost is about 75%of that of the conventional AC systems. In winter, when latent load of the building are 5%,10%and 15
