Civil Engineering Reference
In-Depth Information
Fig. 12.7
Theoretical COP versus load temperatures for heat pumps
In HVAC applications, heat pumps have evaporators in direct contact with the
outside air, which serves as energy source during the cold season. In the hot season,
the same air source can provide cooling through a reversing valve. Figure
12.8
shows how the refrigerant flows inside the same components in heating and in
cooling modes. Note that in the heating mode the outside heat exchanger works as
evaporator (connected with the compressor inlet) and the inside exchanger works as
condenser. In the cooling mode, the outside heat exchanger becomes the condenser
and the inside exchanger becomes the evaporator (connected with the compressor
inlet).
12.10 Practical Examples
Two examples of energy saving are here presented.
The first refers to the replacement of an absorption system by a rotating com-
pressor system in a site where waste heat streams are not available, so that all the
heat needed by the absorption system must be supplied by means of fuels.
The second concerns heat recovery from condensation and lubricant oil cooling,
which is a possibility always present, but exploitable only when end users really
need heat at low temperature.
