Clothes dryers are widely used in American and European homes; in particular

specific independent heat-pump dryers are used in European homes. Independent heat-pump dryers feature high efficiency

low power consumption

and clothes protection properties. As a result

they are increasingly being favored by consumers in China. Currently

the mainstream refrigerant used in heat-pump dryers is R134a

belonging to the A1 class and featuring low chronic toxicity and zero flammability; additionally

its maximum Global Warming Potential (GWP) is 1 430. Meanwhile

natural refrigerant R290 belongs to the A3 class featuring low chronic toxicity; it is flammable and can be explosive

and its GWP is lower than 20. This study is performed based on natural refrigerants R290 and R134a; their physical and thermodynamic properties are compared to optimize the system design of a heat pump clothes dryer. Subsequently

the performance of a heat pump clothes dryer using those refrigerants is analyzed. The final system design features an evaporator with φ7 mm diameter copper tubes and hydrophilic plain fins with a fin spacing of 2.2 mm. The condenser features φ5 mm diameter copper tubes and hydrophobic plain fins with a fin spacing of 1.5 mm. An 8.1 mL displacement R290 compressor is used

and the throttling device is a capillary tube with φ1.0 mm diameter and 820 mm length. The results indicate that using R290 in the heat pump system of the clothes dryer satisfies the requirements of international

national

and European standards of the A3 class refrigerant charge limit

implying that if the maximum charge amount of the A3 class refrigerant does not exceed 0.15 kg

the room volume is not restricted. When the R290 charge amount is 0.15 kg

the heat pump dryer energy efficiency index is 23.0

thus achieving the highest level (i.e.

A+++) of the current European energy efficiency standard for clothes dryer.