As shown in Fig. 1(a), the light lines denotes the water tubes
while the dark lines designates the refrigerant tubes. When showering,
the incoming tap water was firstly pre-heated by the SDW,
and hence part of the waste heat was recovered when the SDW
passed through the WHED, which was installed under the user.
After pre-heated in the WHED, the tap water was divided into
two paths. In one path, the water was heated by R134a in the
HWT. While in the other path, the water was introduced into the
water mixing valve to regulate the shower water temperature.