H4-VH17-B se can be analyzed and evaluated in terms of maxi Helical gear units H4

Flender/Flender Gear Units/Helical gear units H4

frigeration sinceno moving parts are involved. However, series of many Peltier thermoelectric couples is needed to produce sufcient heat exchange for horticultural needs, since each couple produces very small amount of heat exchange. The thermoelectric coolers need directcurrent source, and systems that operate on 1- source or from 1- car batteries havebeen built (. Some systems have capacities of up to 3.2 kW of air conditioning (.To make the system as efcient as possible, heat transfer surfaces that operate in eithergas or liquids are used. For gas systems, the heat transfer component consists of ns to increase the surface area and fans to increase the convective heat transfer rate. Liquid systems use pumps to circulate uid over the heat transfer surface. Apart from the fansor pumps that are used to increase the heat exchange, the system does not have parts that can wear out or generate noise. There is no refrigerant; thus there is no concern about toxicity, corrosiveness, chemical stability, and ammability that may occur in conven-tional vapor recompression systems. The main disadvantage of thermoelectric cooling is that it has low coefcient of performance (: the ratio of heat extracted divided by the necessary energy input to achieve the heat removal. Although thermoelectric cooling has not been extensively usedas source of refrigeration for cooling or storage of fruits and vegetables, it offers manyappealing advantages that may incite further development. 3.6 Calculating Refrigeration Requirements The amount of refrigeration that is required for cooling or storage is often expressed in kilowatts or tons of refrigeration. By denition, tonof refrigeration is the amount of heat absorbed in 2 by ton of ice melting at 0 . One ton of refrigeration is equivalent to 1 6 kJ /H1(1,0 Btu /H. The refrigeration load for storage can be calculated after accounting for all the sources of heat to be removed. There are three main sources of heat: () the produc