Feasibility study of R134a/R404a cascade heat pump cycle in heat pump dryers with electrical heaters at low temperatures

Jeong, Ji Woo; Lee, Young Lim

doi:10.1007/s11630-015-0809-8

Cited by 4 publications

(2 citation statements)

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“…y The average COP is around 2.6 under an outdoor air temperature range of -10 to 20 °C; this means the energy efficiency of the cascade cycle is more than 2.6 times higher than that of the electric heater used in the conventional single-stage cycle. The energy efficiency of the cascade cycle without a solar collector showed COP of 1.84-2.11 [4]. y The heating capacity of the condenser increases while the cooling capacity of the evaporator remains almost unchanged as the temperature of the drying chamber rises.…”

Section: Discussionmentioning

confidence: 99%

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Experimental study on cascade heat pump dryer with a solar collector under low temperature outdoor air environment

Jang

Lee

2018

THERM SCI

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A heat pump dryer can save more energy than other dryers since its drying efficiency is 2-3 times higher than that of other types of dryers. However, the lower bound of evaporating temperature for an R134a heat pump cycle ranges from 5 to 10 °C, when the outdoor air temperature closely approaches the evaporating temperature, it experiences reduced efficiency and ultimately becomes inoperable. To address this issue, a cascade heat pump dryer equipped with a solar collector was considered in order to examine the operability and efficiency of the heat pump cycle, depending on changes in the outdoor air temperature in wintertime. The changes in cascade cycles, depending on the temperature in a drying chamber, were also observed. The results showed that the average coefficient of performance (COP) of the cascade heat pump dryer was approximately 2.6 under the temperature range of -10 to 20 °C. An electrical heater whose COP is less than one should be used in that temperature range. It was also found that COP of the dryer increased by approximately 35% when using a solar collector under a low outdoor air temperature environment.

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Section: Discussionmentioning

confidence: 99%

“…Because of this problem, the drying chamber is heated first to a certain temperature, say 30 °C, using an electric heater at the initial stage of the drying process [4] before operat- ing the heat pump dryer. The related electrical power consumption results in reduced energy efficiency.…”

Section: Introductionmentioning

confidence: 99%