Page 327 - Defrosting for Air Source Heat Pump

322 Defrosting for Air Source Heat Pump

2.0
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% 1.84%
( 1.8
t
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c 1.6
l
a
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n
i
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o
c
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i
f
l
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d 0.5%
a
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n
o 0.2%
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p
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0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
System operating duration (year)
Fig. 10.14 Proportion of additional first cost in total cost in the 15 operating years.
Case D4. The total difference was about $798.89, which accounts for about 9.88% of
the total running costs in the heating seasons in Case D3. Obviously, after the valves
were installed on the multicircuit outdoor coil, the total running costs in the two
heating seasons of the new ASHP unit could save nearly 10%. In the total running
cost in two cases, the running cost in heating season without frost formation accounts
for about 40%, and heating season with frost formation about 60%. This results from
their operating durations, at 16,200 h and 21,459.38–21,290.63 h. The electricity costs
on frosting were 28,893.29 CNY in Case D3 and 26,035.71 CNY in Case D4, respec-
tively, with a difference of 2857.58, or 9.89% of the cost in Case D3. However, the
ratios of the electricity cost on frosting in the total running costs in the heating season
with frost formation were nearly the same, at 53.89% in Case D3 and 53.58% in Case
D4. Therefore, after the valves were installed, the running costs at all stages were
decreased. The difference was not at any one stage.
Fig. 10.10 shows the accumulated total costs in the two cases in the 15 operating
years. The total values were $11,615.28 in Case D3, and $10,838.93 in Case D4,
respectively. Their difference was $776.36, which accounts for about 6.68% of the
total cost in Case D3. This directly reflects that the economic performance of the
new ASHP could be effectively improved after valves were installed on the outdoor
coil. With nearly the same first costs, the total costs in the two cases were mainly
decided by their running costs. The running cost in Case D3 was $10,416.12, but
$9617.25 in Case D4. That means the running cost could decrease by as much as
$798.87, or 7.67%, after the valves were installed. In the two cases, the running costs
in cooling season were the same, but the ratio increased from 20.08% to 21.51% after