• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.11 no.4
• /
• pp.22-27
• /
• 2015

Quality characteristics of Shiitake mushroom using two types of dryers, energy-efficient heat pump hot-air dryer and electric heater hot-air dryer were compared. Energy consumed during drying by heat pump hot-air dryer and electric heater hot-air dryer were 22.8 kWh and 28.9 kWh, respectively. Total polyphenol content of heat pump hot-air dryer and electric heater hot-air dryer after drying were $290.55{\pm}10.56ppm$ and $192.99{\pm}6.53ppm$, respectively. No differences were observed between dryers in reconstitution rate and browning ratio after drying. Also, there were no differences between dryers in color value and ${\Delta}E$ value after drying. Shiitake mushroom drying at $45^{\circ}C$ by heat pump hot-air dryer was proved to be more efficient in energy consumption than by electric heater hot-air dryer.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.14 no.4
• /
• pp.7-12
• /
• 2018

Energy performance of electric heater and geothermal source heat pump type hot air dryers are compared in this study. For set temperatures of $30^{\circ}C$, $35^{\circ}C$ and $40^{\circ}C$, radish is dried from initial mass 60 kg until it gets 5 kg, where the difference equals the amount of water removed. As set temperature is increased, drying time is shortened for both electric heater and heat pump types, however energy efficiency is decreased due to increasing electricity consumption. Moisture extraction rate(MER) of electric heater is 2.58~2.84 kg/h, and for heat pump type 2.56~2.71 kg/h, showing little difference between the two types. Specific moisture extraction rate (SMER) of electric heater is 0.94~0.96 kg/kWh, and for heat pump type 1.72~2.21 kg/kWh. SMER of heat pump type is greater by 0.78~1.25 kg/kWh than the electric heater hot air dryer, which is 1.8~2.3 times better in terms of energy efficiency.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.11 no.4
• /
• pp.1-6
• /
• 2015

In this study, energy performance of two types of food dryers which are electric heater and heat pump is studied experimentally. With drying chamber temperatures controlled at 45, 50 and $55^{\circ}C$, sliced radish is dried from an initial mass of 90 to final 7 kg. Moisture content, drying time, total power consumption, MER (moisture extraction rate, kg/h) and SMER (specific moisture extraction rate, kg/kWh) are measured and analyzed. As the drying chamber temperature is increased, drying time is shortened but energy efficiency is reduced for both types. For an electric heater dryer, the effect of chamber temperature on drying time is significant but less significant on energy efficiency. For a heat pump dryer, the dependence of chamber temperature on drying time is weak but strong on energy efficiency. Temperature levels have little effect on electric heater dryer performance but strong effect on heat pump dryer which operates on a vapor compression refrigeration cycle. The energy performance of the heat pump dryer is superior with an average SMER of 2.175 kg/kWh which is 2.22 times greater than that of the electric heater dryer with SMER of 1.224 kg/kWh.