1、PDF外文：http:/ 1 外文资料 Performance of ice storage system utilizing a combined partial and full storage strategy Abstract A combined system is a new thermal storage strategy adopted in this study with which the two other knownstrategies namely, partial and full load, are compar
2、ed. The results revealed that the combined system requireslarger equipment size than that required by partial system to satisfy the same cooling load. Factors F and F thatp fmay be multiplied by the daily average cooling load to determine the optimum chillers size for a combined systemare found. The
3、se factors are applicable for any cooling load and are based on a given chiller condensing andevaporating condition as used in this study. These factors are found to vary with the number of on-peak hours.Combined strategy required chiller size was found to decrease with decrease in on-peak period, h
4、ence theoptimum chiller size for this new strategy was found to occur at zero on-peak hours, and i.e., when the combinedsystem starts to operate as a partial strategy system. Keywords: Ice storage system 1. Introduction Thermal storage is the temporary storage ofhigh or low temperature e
5、nergy for later use. Airconditioning system that employs thermal stor-age equipment incorporates two strategies, thepartial and full load. For either of these strategies, investigations were made to determine thepossible saving in chiller size as compared withconventional cooling system. The partial
6、 andfull storage strategies were previously studiedindependently and the results obtained hadshown that the chiller size required in partialstrategy 河南科技大学毕业设计 2 is smaller than that required in fullstrategy to satisfy the same cooling load. In this study a new strategy is ad
7、opted andinvestigated for chiller size determination. Thisstrategy is named as a combined strategy systemwhich includes both, the partial and full load,operating simultaneously. Hence, two sets ofchillers are used in this new system, the first setoperates continuously as a partial system and theseco
8、nd set operates during the off-peak periodas a full system helping the first set chillers tomeet the cooling load and charge the thermalstorage reservoirs. The aim of this study is to find the optimumchiller size in a combined strategy system and tocompare it with that of partial strategy at d
9、ifferent on-peak hours to meet the same coolingload. Also, a relation between the optimumchiller size and cooling load is to be determinedfor general use at a set of governing conditions. To illustrate the combined strategy merits,three different case buildings with differentcooling loads are
10、investigated. 2. Theory 2.1. Assumptions In this study, the following assumptions havebeen considered: 1) Air-cooled chillers with reciprocating compressors. 2) Evaporating pressure and temperature areconstants. 3) Refrigerant leaving the condenser and entering the expa
11、nsion valve is saturated liquid. 4) Vapor leaving the evaporator and enteringthe compressor is saturated. 5) Refrigerant R-22 is used. 2.2. Conventional cooling system chiller In order to show the merits of a thermal storage system, the conventional system chillerscapacity ha
12、s to be determined for comparison.In common practice the size of these chillers isselected 河南科技大学毕业设计 3 equal to the maximum cooling loadwhich happens to be 28.67, 21.82 and 22.13 KWfor cases (1), (2) and (3) respectively. 2.3. Combined strategy system In a combined system wh
13、ere two sets ofchillers operate in partial and full strategies atthe same time, it is important to find the minimum combination chiller size that will satisfythe cooling load at a set of conditions. Theseconditions are the evaporating and condensingpressure and temperature and the number of on-peak
14、hours during which only the partial chilleris kept running. The procedure adopted in thisstudy in finding the minimum chiller size maybe summarized as follow: (a) An initial assumption of the partial chillersize is to be made. The chiller size thus assumedshould be related, some how, to the co
15、oling load.Two distinct values of the cooling load are themaximum and the average value and the later ischosen in this study. Hence the initial partialchiller size will be the average cooling load multiplied by a certain, arbitrarily selected, factor (Fp ). (b) Since air-cooled chiller is use
16、d, its condensing temperature would vary according toinlet ambient air temperature. Therefore the initial partial chiller size would be based on thecondensing temperature at which maximumcooling load occurs. (c) Chiller capacity is then determined hourlyand for the daily cycle at the different
17、 existingcondensing temperature. (d) The difference between the daily cyclecooling load and the daily total partial strategychiller capacity would be met by the full strategy chiller. The size of this chiller is assumed tobe equal to the average cooling load multipliedby a factor (F) and must equal to the differenceindicated above. If this condition is not satisfiedthen another value of (Ff) is selected. (e) The combined strategy chiller sizeobtained by the initial run with the assumed (Fp)and calculated (Ff) may not be the
