ASHRAE Journal - January 2020 - 52

TECHNICAL FEATURE

FIGURE 13 Unit 1 power variation under summer refrigeration condition.

FIGURE 14 COP evaporation chart in winter 2015-2016.

COP Evaporation in Winter

Summer Unit 1 Power

FIGURE 15 COP evaporation profile in summer 2016.

as it is the busy period of the semester. Therefore, the
indoor temperature dropped back to the normal working temperature after the beginning of August. In summer, the overall power transitions were within the range
of 14 to 35 kW and oscillated around 16 kW from July 1 to
August 1. When the building space was in use as well as
the working temperature, the power remained stable.
The variation of COP evaporation overtime (2015 to
2016), as shown in Figure 14, in the winter, reached the
maximum of 3.160 and the minimum of 2.744 both in
January 2016, with an average value of 2.982, and both
fluctuated between 2.6 and 3.2.
Figure 15 demonstrates the gradual variation of COP
with time in summer 2016. Initially, the system's operation showed a high COP up to 8.377 especially in the
summer, but due to the phenomenon of cold and heat
accumulation, the COP efficiency was gradually identified, and which was also seen in the low-temperature
trend shown in Figure 4. Consequently, COP evaporation value, with an average value of 5.254, reached a
maximum of 8.377 in July 2016 and a minimum of 2.451
in August 2016 both fluctuated between 2 and 9. This
indicates that COP does not remain constant during the
cooling or heating season, but tends to decline after an
instantaneous accumulation of cold and heat.
In Figure 16, as the accumulated electric power and
outdoor monthly temperature curve of the heat pump
system per month for the heat pump unit is shown from
November 2016 to October 2017, it can be seen that highest outdoor month average temperature was 27°C (81°F)
as the minimum recorded was 12°C (54°F). In December
2016, the maximum value of the electric power load
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COP Evaporation in Summer

was recorded and thermal energy production was
28 111.8 kWh, which was in line with the lower temperature distribution curve. Obviously, the power required
in winter was larger than that in summer, although the
lowest temperature was generated in January 2017, and
only required a low-temperature operation. Similarly,
the accumulated electric power of the heat pump system per month in the heat pump system was around
the highest point in the summer of July 2017, which was
normal for refrigeration and was in accordance with the
average monthly temperature for that year. However, in
May, the heat pump system needed to have a low electrical load, because the general temperature of this month
was relatively comfortable in cold regions. As a result,
the heat pump unit maintenance period was mainly
performed, and the operating power was only 274 kWh
in this particular month.

Conclusion
The following conclusion can be made from the results
of the study. This article proposed a method to improve
the difference between cooling capacity and heating

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ASHRAE Journal - January 2020

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