Which one of the following is correct relation between (COP)HP and (CO...
The efficiencyof a refrigerator is expressed in terms of the coefficient of performance (COP), denoted by COPR. The objective of a refrigerator is to remove heat (QL) from the refrigerated space. To accomplish this objective, it requires a work input of Wnet,in. Then the COP of a refrigerator can be expressed as
COPR=(desiredoutput)/(requiredinput)=Q(L)/W(net,in) ---(1)
This relation can also be expressed in rate form by replacing QL by QL and Wnet, in by W(net,in).
The conservation of energy principle for a cyclic device requires that
W(net,in)=QH−QL(KJ) ----(2)
Then the COP relation becomes
COPR=QL/(QH−QL)=1/(QH/QL−1) ----(3)
Notice that the value of COPR can be greater than unity.
Another device that transfers heat from a low-temperature medium to a high temperature one is the heat pump. Refrigerators and heat pumps operate on the same cycle but differ in their objectives. The objective of a heat pump, however, is to maintain a heated space at a high temperature. This is accomplished by absorbing heat from a low temperature source, such as well water or cold outside air in winter, and supplying this heat to the high-temperature medium such as a house.
The measure of performance of a heat pump is also expressed in terms of the coefficient of performance COP_HP, defined as
COP(HP) = (Desiredoutput)/(Requiredinput)=QH/W(net,in) --(4)
This can also be expressed as,
COP(HP) = QH/(QH−QL) = 1(1−(QL/QH)) --(5)
Comparing equation 3 and 5 reveals that,
COP(HP) = COP(R) + 1
for fixed values of QL and QH. This relation implies that the coefficient of performance of a heat pump is always greater than unity since COPR is a positive quantity. government policy or in trade arrangements, and by development of irrigation, roads, and other infrastructures.