DESIGN AND PERFORMANCE ANALYSIS OF A METAL HYDRIDE AIR-CONDITIONER

The design and performance aspects of a 3⋅5 kW (1 ton) cooling capacity metal hydride air-conditioner working with a ZrMnFe/MmNi_4⋅5Al_0⋅5 pair are presented. The analysis is based on the heat transfer and reaction kinetics of coupled beds containing ZrMnFe alloy on the hot side and MmNi_4⋅5Al_0⋅5 on the cold side. The effects of important design and operating parameters, viz. cycle and delay times, bed thickness, effective thermal conductivity, air velocity and operating temperatures, on system performance are studied. The performance of the system is characterized by the mass of the alloys required and the COP. The results show that the initial and running costs of the system depend mainly on the internal and external heat transfer characteristics of the hydride heat exchangers. It is shown that a 1 cm ID tube, a cycle time of 3 minutes, an effective thermal conductivity of about 2⋅5 W m⁻¹ K⁻¹ and air velocity of about 3 m s⁻¹ result in optimum performance in terms of alloy inventory and COP. © 1997 by John Wiley & Sons, Ltd.