DESIGN OF SOLAR-DEHUMIDIFICATION WOOD DRYING KILN CHARACTERIZED BY HIGH-CAPACITY AND TEMPERATURE

Solar-dehumidification wood drying kilns attract more and more interes t due to their energy saving characteristics. However, such dryers are only available for small effective drying volume capacities, less tha n 30 m(3), and for low drying temperature under 65 degrees C, for Chin ese domestic products. In fact, wood drying kilns over 60 m(3) and hig h drying temperatures up to 95 degrees C or even higher are commonly d esired from economic and process technology points of view. For instan ce, if the drying temperature is below 60 degrees C, a long drying per iod will result in high operational costs and may also cause mould as well colour changes on the lumber surface. It is also known that the a nti-decay ability of the seasoned lumber is thus reduced. As such, the design of the solar-dehumidification wood drying kiln with an effecti ve drying volume capacity of 60 m(3) and a drying temperature up to 95 degrees C was made. Two compression processes for dehumidification an d heat pump systems were adopted. The refrigerant of R(I42b), which ha s low RODP and RGE, was utilized as the actuating medium. The values o f COP, PER and SMER were 4.42, 1.19 and 3.08 kg (H2O)/(kWh) for the de humidification system. The values of COP and PER were 3.05 and 0.824 f or the heat pump (heat supply) system. The averaged total COP and PER over the both were 3.74 and 1.01 respectively. By comparison with a co nventional wood drying kiln, the economic evaluation showed that the e xtra investment on solar and refrigeration systems can be paid back wi thin one and half years of operation in due cause of energy savings. T he design also possesses the advantage over the existing dehumidificat ion wood dryers, due to its less adverse effects on the environment.