Page 309 - Defrosting for Air Source Heat Pump

304 Defrosting for Air Source Heat Pump

period that was accepted by the customer. Using a lifetime of 20 years for ground-
coupled and air-coupled heat pump systems, their performances were compared based
on the experimental COP results by Esen et al. [14, 15]. The economic analysis clearly
shows that the ground-coupled system is economically preferable to the air-coupled
one. In addition, Dong et al. discussed the economy of an ASHP unit with a PCM-TES
system added to improve its RCD performance. It was concluded that before the
replacement of the PCM in the TES system, using the novel RCD method, the running
cost could save approximately $97.47 over 7 years of service life. Recently, a
technoeconomic analysis of ASHP applied to space heating in northern China was also
carried out, with the pollution emission considered [16]. Although the authors
neglected the unavoidable frosting/defrosting problem in northern China, the low-
temperature ASHP heating system was demonstrated to have a better economical
performance than a coal-fired boiler, a gas boiler, a direct electric heating mode, or
combined heat and power generation systems.
Many ASHP unit studies on energy performance improvement have been reported,
although only a few of them considered economic performance [17, 18]. To analyze
the economic performance of the new ASHP unit, an economic analysis on its novel
frosting/defrosting operations is given in this chapter. First, the two conditions, with
and without the valves installed in the multicircuit outdoor coil of an ASHP unit, were
analyzed, with the fundamental frosting and defrosting state assumptions clearly
listed. This is followed by an investigation on the four working conditions of the
ASHP unit, with the water-collecting trays placed under each circuit to take away
the melted frost before flowing into the downside circuit further considered. This
study is helpful for the relative technologies applied in the industry and the real mar-
ket. The conclusions given in this chapter can also play a role in the pricing or gov-
ernmental subsidy of ASHP units.

10.2 The influence of the refrigeration adjustment valve

To analyze the economic performance of the new ASHP unit, with valves installed in
its multicircuit outdoor coil, an economic analysis on its novel frosting/defrosting
operations is given in this study. First, the results of the designed frosting/defrosting
experiments will be presented, as well as a series of assumptions given. To clearly
show the frosting and defrosting influence on the economic performance of the ASHP
unit, a typical city in severe cold regions in China will be chosen as an example. This is
followed by the development of economic analysis equations, which will be used in
cases with and without valves installed. After the results are calculated in this study,
the proportion of costs at different stages and payback periods will be analyzed.

10.2.1 Methodology
In order to carry out this economic analysis, the methodology was first illustrated in
Fig. 10.1. As shown, the first step is an experimental study with an ASHP unit selected
and a three-circuit outdoor coil specially made. Then, the two typical conditions were