Environmental Engineering Reference
In-Depth Information
Fig. 5.3
Heat that can be obtained from combustion, electrical resistance heating and a heat pump
from 100 units of fuel. Losses shown are typical for the devices
One device (evaporator) is at a much colder temperature than the environment so
that heat transfers from the environment to the evaporator. Another device (heat
exchanger) is at a temperature that is much hotter than the environment so that heat
transfers from the heat exchanger to the target area or fluid. In Fig.
5.4
, the environ-
ment supplies heat (
Q
C
) to the evaporator to vaporize liquid CO
2
so that it can be
compressed and the hot CO
2
supplies heat (
Q
H
) through the heat exchanger so that
it can be used for making hot water. The heat pump achieves its high efficiency by
using heat available in the environment to recycle the CO
2
. The choice of the work-
ing fluid and the specification of the conditions of the devices are important for
achieving the desired results in any heat pump system. Once the concept of the heat
pump is understood, it can be seen that there are many applications.
5.3.4
Eco-Cute Hot Water Heater
The Eco-Cute hot water heater shown in Fig.
5.4
is a special case of a heat pump sys-
tem that uses CO
2
as the working fluid for making hot water. In Fig.
5.4
, electrical
work is input to a compressor that pressurizes the CO
2
. Pressurization of the CO
2
