外文翻譯--熱帶地區(qū)地板空調(diào)系統(tǒng)的室內(nèi)空氣品質(zhì)和熱舒適性的調(diào)查 英文版

1、<p>　　編號： </p><p>　　畢業(yè)設計(論文)外文翻譯</p><p><b>　?。ㄔ模?lt;/b></p><p>　　院 （系）： 職業(yè)技術(shù)學院 </p><p>　　專 業(yè)： 機電一體化工程 </p><p>

2、　　學生姓名： ****** </p><p>　　學 號： **自考準考證號** </p><p>　　指導教師單位： 職業(yè)技術(shù)學院 </p><p>　　姓 名： ***** </p><p>　　職 稱： *****

3、 </p><p>　　2012年 10月 8日</p><p>　　Indoor air quality and thermal comfort studies of an </p><p>　　Under-Floor air-conditioning system in the tropics</p><p><b>

4、　　Abstract </b></p><p>　　This paper reports thermal comfort and indoor air quality (IAQ) studies of an under-floor air-conditioning (UFAC) system in hot and humid climate. Thermal comfort parameters w

5、ere measured at predetermined grid points within an imaginary plane to predict the airflow pattern of the supply air jet as well as to determine the occurrence of thermalstratification in the office space. Fanger's [

6、Thermal Comfort Analysis and Applications in Environmental Engineering, McGraw-Hill, New York, 1970] therma</p><p>　　the primary air jet.</p><p>　　Keywords: under-floor air-conditioning systems

7、; thermal comfort; Indoor Air Quality; Singapore; office, field trips</p><p>　　1 Introduction This concept has been used for many years the concept of cold air from the raised floor computer room. How

8、ever, these areas rarely occupier and no real attempt to apply for the same air standard office environment comfortable movement. For example, in the early 1960s, the Federal Republic of Germany, (UFAC) under-floor air-c

9、onditioning system is the first to introduce high heat production room, such as the electric light bulb factory, the drying device and data processing c</p><p>　　1, concentration data collected particles and

10、 carbon dioxide; </p><p>　　2, correlation analysis and simple linear regression of variables, that: 2.1, particle counting, and the air flow rate and 2.2, carbon dioxide and an air flow rate.

11、</p><p>　　2 UFAC system-a review</p><p>　　An UFAC system is comparable to a displacement ventilation (DV) system in that both system sometimes supply cold air from diffusers that are mounted on

12、 the floor.However,for the latter system,supply air can also be supplied through diffusers that are mounted in walls near the floor where the return air is subsequently exhausted through the ceiling grilles,as shown in F

13、ig. 1. While DV system generally supply lower velocity air with the goal of minimising mixing and maximising displacement and str</p><p>　　2.1. Thermal stratification</p><p>　　The aim of air dif

14、fusion in air-conditioning system is to create the proper combination of temperature,humidity and air motion in the occupied zone of the conditioned space. Nevertheless,a floor-based air-conditioning system is often foun

15、d to be associated with large thermal gradients (thermal stratification) between the feet and the head as well sa local thermal discomfort due to draft [8].In the case of dissatisfaction as a function of the verti

16、cal air temperature difference between h</p><p>　　Temperature gradient refers to the difference between temperatures at any two points. ASHRAE Standard 55- 1992 [10] recommends that the ma

17、ximum temperature gradient should not exceed 3 °C. Therefore, an ideal con- dition would be uniform room temperature from the floor to about 1800 mm above the floor [11]. However, a gradient of 2 °C should be

18、acceptable to about 85% of the occupants to remain thermally comfortable. </p><p>　　A field study involving the installation of desktop task/ ambient air-conditioning system at 42 selected locations wi

19、thin three San Francisco office buildings revealed higher occupant satisfaction levels in terms of thermal, acoustic and air quality [12]. </p><p>　　Hanzawa and Nagasawa subjected 26 people in a test

20、 room that utilised the UFAC system in which the return grilles were mounted in the ceiling [13]. These people were then surveyed on the sensation of draft and air movement. The air velocity around them was also

21、 measured. It was found that the average room-air temperature differences between 0.1 and 1.1 m above the floor in the occupied zone were around 1 °C. In addition, it is found that the system could provide little dr

22、aft ris</p><p>　　and Nielsen [8]. </p><p>　　Akimoto et al. [15] conducted a comprehensive study on such system in an experimental chamber located in a controlled environment chamber with the

23、return air leaving through the ceiling grilles [15]. Temperature distribution tests were carried out to investigate the effects of lighting, occupants, electrical equipment, walking and change of air volume for thermal

24、 stratification. In addition, qualitative and quantitative studies for the system were performed to investigate the airflow charac</p><p>　　2.2. Thermal comfort indices </p><p>　　A practical ap

25、proach to assessing thermal environments for the comfort of the occupants is provided by Fanger [16]. A thermal sensation index was developed to predict the mean thermal sensation vote on a 7-point standard scale

26、 for a large group of people. The index depends on the four thermal environmental variables (air temperature, relative humidity, mean radiant temperature (MRT) and relative air velocity), the activity level and the clo-v

27、alue of the clothing worn by the occupants. </p><p>　　Meanwhile, it seems more meaningful to state what percent of persons can be expected to be decidedly dissatisfied than just giving the pre

28、dicted mean vote as an expression for the thermal environment. Therefore, the PPD curve can also be used as a basis for an evaluation of thermal environments. </p><p>　　Some of the researchers have conducte

29、d investigations on the effect of such system on the thermal sensation of the occupants. For instance, Yokoyama and Inoue evaluated the performance between the UFAC system and the ceilingsupply air-conditioning

30、system [1]. The evaluation was carried out by measuring the room environment in a test chamber and by surveying sensation responses from ques- tionnaire in the operating offices. PMV values were calculated an

31、d the results reveal</p><p>　　2.3. Indoor air quality </p><p>　　Air quality in offices has been a major concern in the past two decades,particularly due to the increasing number of reports

32、on the sick building syndrome. Although several research efforts have been carried out, most of the investigations on the IAQ are performed on the conventional ceilingsupply air-conditioning systems. In the case of

33、UFAC systems, limited information is available in the literature [12]. </p><p>　　Although air quality is not directly considered a thermal comfort parameter, it is closely related. For example, high relative

34、 humidity in the office space not only brings about occupants' discomfort but also promotes the growth of moulds and fungi. On the contrary, humidity level less than 30% can lead to increased airborne dust levels as

35、well as static electricity, which in turn may lead to comfort and IAQ problems. Under the ENV guidelines [18], it is recommended that the relative humidity le</p><p>　　Carbon dioxide is commonly used as

36、 an indicator of reduced air quality and ventilation efficiency. In the occupied rooms, CO2 will increase if the air supply rate per person is inadequate. It is therefore an effective surrogate for the adequacy of

37、 fresh air being brought into a building. Studies [14,15,19] have shown that the UFAC system, when compared to the conventional system, provides for better ventilation efficiency. This is mainly due to the fact th

38、at the partially encl</p><p>　　There is a concern for the suspended particulates that follow the supply air stream from the floor. The size range of concern when human health effects and IAQ are cons

39、idered is from 0.1 to 10 mm in aerodynamic diameter. Small particles that reach the thoracic or lower regions of the respiratory tracts are responsible for most of the adverse health effects. Local IAQ guidelines [

40、18] recommend the limit of 150 mg/m 3 for suspended particulate matter. Particulate matter is easily c</p><p>　　Advantages of the floor-based system enumerated by most of the proponents include flexibility

41、, cost-saving in the long run, individual control over the temperature, better air quality and thermal comfort in the workplace. On the contrary, some have raised doubts on the effectiveness of the system. For instance,

42、an under-floor system with the return grille at the ceiling may cause local thermal discomfort and large temperature gradient whereas the one with return air exhausting through the floor </p><p>　　3 UFAC sy

43、stem description </p><p>　　UFAC systems come in different designs although the location of the return air grille is limited to be only either on the floor or the ceiling plenum. Nevertheless, the test system

44、 here is designed with both the supply and return on the raised floor. It is now intended to provide a general description of the system and an understanding of the way the air is distributed in the occupied zone. </

45、p><p>　　The UFAC system directly makes use of the floor void as a plenum for the distribution of air. Each floor is fitted with raised access flooring and steel encapsulated floor panels. Beneath this, movable

46、airtight baffles delineate the supply and return air channels. A conditioning unit, which is usually located in the office, conditions the outside air that is brought into the building. The air is then distributed under

47、the floor to the fan terminal units (FTUs), which ventilate individual </p><p>　　Each conditioning unit is a vertically arranged air handling unit containing a filter, copper pipe/aluminium fin

48、 cooling coils, direct drive fans and comprehensive controls system. The unit is made with self-supporting steel framework clad with acoustically lined steel panels. In addition, it is finished in standard powder coat fi

49、nish and stands on a purpose made base frame. </p><p>　　The FTU draws air from the plenum and introduces it into the space above in accordance with the requirements of their own on-board controls system. In

50、addition, a multi-functional control permits personalised temperature and airflow control. The FTU measures 600 mm in length and 300 mm in breadth and is recessed into the floor to offer greater space gain. It can replac

51、e an access floor tile anywhere in the room and can be used as part of the walking surface.</p><p>　　Each unit also contains twin scroll fans driven from a single motor, an open/shut control damper, an opti

52、onal electric heating coil, and a self contained on-board control system. The units require no ductwork connections and are easily relocated in a matter of minutes. </p><p>　　Return grilles constructed in th

53、e same material as those used for the FTU are 600 mm long and 150 mm wide. They are positioned in the floor over the return plenum to permit the return of secondary room air to the conditioning unit for re-conditioning.

54、They comprise of solid parallel aerofoil blades supported with transverse bars and coated in neutral silver anodised finish as standard. </p><p>　　The grilles have the same height adjustment feature as the F

55、TU grilles for easy alignment with the final floor covering and may be supplied with a collecting tray, opposed blade control dampers and acoustic attenuator as additional options. </p><p>　　4 Description o

56、f test site </p><p>　　The building in which the experiment is carried out is a double-storey 6-year-old single unit factory with a gross floor area of approximately 5000 ㎡. However, the area that utilises t

57、he UFAC system is only about 300㎡ and this is found in the corporate office, shown in Fig. 2. </p><p>　　The total number of staff working in the office does not exceed 10 persons. In other words, every occup

58、ant occupies an approximate area of 30㎡. The UFAC system is not equipped with a proper outside air provision and is dependent on infiltration during opening and closing of the doors. For the remaining of the building,i.

59、e.the marketing department and reception area,conventional ceiling-mounted air-conditioning system is used. As for the production floor, it is not air-conditioned. Instead, </p><p>　　5 Research methodol

60、ogy </p><p>　　A methodology involving the measurement of thermal comfort parameters, chemical and particulate contamination is adopted in this research study. The office space that utilises the UFAC system

61、is divided into three zones namely Zones A, B and C with each zone served by a different .</p><p>　　conditioning unit, as shown in Fig. 3(a)-(c). As it is not within the scope to study the airflo

62、w pattern, air quality and hermal stratification at every location where the floor grille exists, two sampling locations were selected from Zones A and B, respectively. Only one sampling location was taken from Zone C, a

63、s this is the only location that is free from obstruction by the furniture. Each sampling location comprises a set of floor diffuser and a return grille in which the supply ai</p><p>　　In the experiment that

64、 was carried out to determine the various thermal comforts and IAQ parameters of the UFAC system, an imaginary plane, consisting of horizontal and vertical gridlines, was set up in the sampling location. Within the pla

65、ne, readings were taken at every grid point as show in Fig.4.</p><p>　　5.1. Measurement procedures </p><p>　　For the measurement of temperature, air velocity and relative humidity, the interval

66、s along the horizontal, as well as vertical gridlines, were set at 0.5 m with the highest point at 2.5 m above the raised floor. Readings were thus recorded at the various grid points using the appropriate equipment acco

67、rdingly. </p><p>　　As for the measurement of dust concentration, the horizontal distance between the supply and return grilles was divided into the intervals of approximately 1.2 m at all the sampling locati

68、ons except Locations 2 and 4, in which the intervals were set at 1.5 m. In addition, at each interval, the </p><p>　　vertical gridline was divided into intervals of 0.8 m, with the highest point at 2.4 m abo

69、ve the raised floor. Measurements of the total suspended particles and PM10 were, therefore, carried out at all the intersection points of the gridlines. </p><p>　　A total of 210 observations each were recor

70、ded for temperature, relative humidity and air velocity in the office space for the five sampling locations. As for carbon dioxide and dust measurements, 32 and 64 readings were noted, respectively. Each measurement for

71、 carbon dioxide and particulate matter was measured for a time period of 15 min. </p><p>　　The following sections describe the various types of equipment that are needed for the field measurement. The resear

72、ch strategy and experimental design will also be </p><p>　　illustrated together with the procedures for data analysis.</p><p>　　5.2. Analytical techniques </p><p>　　Readings for al

73、l the parameters are tabulated according to the location as well as depicted in the form of contours. The results are subsequently used for analyses and comparison against guidelines and standards. </p><p>　

74、　It will be inadequate to assess the level of thermal comfort in the office space if it is only based on the physical quantities obtained from objective measurement. To enhance the preliminary findings, simulation can al

75、so be carried out to detect how the occupants feel in the indoor environment. One method is to adopt the thermal index developed by Fanger [16]. This involves the computation of PMV, which then leads to the determinatio

76、n of values for PPD. </p><p>　　In this research, the values of PMV are computed for all the grid points in the five sampling locations. In order to find out the PMV for a particular grid point, readings coll

77、ected on temperature, relative humidity and air velocity at the similar point are employed in the comfort equation [16]. MRT is assumed to be equal to the dry bulb temperature. Metabolic rate is assumed to be 50 kcal/h㎡a

78、nd this indicates an occupant who is quietly carrying out some clerical work in a sedentary position. Th</p><p>　　Statistical tools are employed to explore whether the values of the primary air velocity, me

79、asured at the grid points, are correlated to the relative humidity and temperature in the room space at those corresponding points. This also includes PMV and PPD. Furthermore, it is speculated that the velocity of the p

80、rimary air jet may also have certain impact on the levels of carbon dioxide and dust particles that are lying in its air path. </p><p>　　Correlation analyses for the five locations are carried out for the fo

81、llowing pairs of variables: </p><p>　　temperature and relative humidity; </p><p>　　temperature and air velocity; </p><p>　　relative humidity and air velocity; </p><p>　

82、　PMV and air velocity; </p><p>　　PPD and air velocity; </p><p>　　particle count (TSP/PM10) and air velocity and </p><p>　　carbon dioxide and air velocity. </p><p>　　As

83、some of the grid points of dust and carbon dioxide measurements do not coincide with the grid points of the velocity readings, mathematical interpolations were carried out for consistency. This enabled the readings for v

84、elocity and dust particles, as well as carbon dioxide, to be subjected </p><p>　　to correlation study on the same basis.</p><p>　　5.3. Instrumentation </p><p>　　5.3.1. Chemical me

85、asurement </p><p>　　An indoor environment monitor is used for the measurement of CO 2. The standard unit comes with sensors for monitoring three basic comfort and ventilation parameters namely carbon dioxid

86、e, temperature and relative humidity. However, in this experiment, the purpose of using such a monitor is to measure the concentration level of carbon dioxide in the various sampling locations. The instrument, employing

87、 a non-dispersive infrared detector, measures the gas within the range of 0-5000 ppm and has </p><p>　　5.3.2. Particulate measurement </p><p>　　The concentration of the suspended particulates i

88、n this experiment is measured using a dust monitor, which has been designed to provide continuous gravimetric measurement of dust as well as virtually any other aerosol and/or particulate-as these materials exist sus

89、pended in the ambi- ent air. In addition, it provides real-time continuous documentation of the size (or aerosol diameter) distributions of these ambient particulates. </p><p>　　This environmental lase

90、r aerosol spectrometer is capable of measuring particles with diameter between 0.1 and 15 mm, with an accuracy of Æ5%. In general, the instrument is suitable for monitoring dust and/or aerosols all the way from the

91、 ultra-low concentration levels of a clean room, to the relatively higher levels commonly encountered in the average workplace. </p><p>　　5.3.3. Thermal comfort measurement </p><p>　　The th

92、ree thermal comfort parameters, namely temperature, relative humidity and air velocity, which are essential for tracing the airflow pattern of the supply air from the UFAC system and also to determine any thermal

93、stratifica- tion in the office space, are measured with the help of two hand-held instruments. The MRT is assumed to be equal to the dry bulb temperature in this study. The hot wire anem- ometer is used specifically for

94、the measurement of the velocity of the supply air from</p><p>　　60 °C with an accuracy of ±0.1 °C.</p><p>　　6 Results and discussion</p><p>　　6.1. Empirical results

95、 </p><p>　　6.1.1. Temperature </p><p>　　The maximum, minimum and the mean temperatures for the five sampling locations are shown in Table 1 and a sample of the temperature results is presented

96、 in Fig. 5. </p><p>　　It is seen that majority of the values fall within the acceptable temperature range of 20-27 °C as stated in ASHRAE Standard 55-1992 [10]. Singapore Standard Code of Practice 13 [

97、27] requires the comfort temperature to be within 23-25 °C while ENV Guidelines [18] recommends temperature range between 22.5 and 25.5 °C for acceptable IAQ. Based on the local standards, the average room temp

98、eratures for all the locations are satisfactory except temperature readings that are near or at the supply dif</p><p>　　The vertical temperature distribution at every vertical axis in the sampling locations

99、is examined so as to determine the extent of the thermal layer, which is a feature of the UFAC system [14]. It is found from the experiment that large temperature gradient usually occurs at the supply diffuser while temp