Energy 28 (2003) 1021–1037 www.elsevier.com/locate/energy A novel approach to determine optimum switching frequency of a conventional adsorption chiller K.C.A. Alam, Y.T. Kang * , B.B. Saha 1 , A. Akisawa, T. Kashiwagi Department of Mechanical Systems Engineering, Tokyo University of A & T, 2-24-16 Naka-Cho, Koganei, Tokyo 184-8588, Japan Received 16 March 2000 Abstract This article investigates the effect of design parameters on the switching frequency of a conventional adsorption chiller with silica gel as adsorbent and water as adsorbate. It is well known that as the cycle time lengthens, the coefficient of performance (COP) rises but the cooling capacity lowers. Optimum cycle time is dependendent on the requirements of COP and cooling capacity. A novel simulation technique that introduces a profit function is employed to determine the optimum switching frequency of an adsorption refrigeration system. The results show that optimum switching frequency is very sensitive to the heat exchanger’s design parameters. The design parameters are characterized by the number of transfer unit, NTU, the Biot number of adsorbent bed, Bi, the aspect ratio, AR, the ratio of the heat exchanger thickness to the radius of the fluid channel Hr, the fluid alpha number, a f-a and the inert material alpha number, a m-a . The optimum switching frequency increases with the increase of NTU, Hr and with the decrease of Bi, AR, a m-a and a f-a .  2003 Elsevier Science Ltd. All rights reserved. 1. Introduction In the promotion of environmentally friendly energy utilization systems, one major goal is to develop CFC-free refrigeration/heat pump systems that utilize waste heat or renewable energy sources. Adsorption cooling systems promise to provide a safe alternative to CFC-basis refriger- ation devices. From this point of view, a number of researchers investigated the possibility of an adsorption heat-pumping/refrigeration system driven by waste heat or by renewable heat sources. * Corresponding author. Present address: School of Mechanical System Engineering, Kyung Hee University, Seochon-ri 1, Yongin- shi 449-701, South Korea. Tel.: +82-331-201-2990; fax: +82-331-201-2990. E-mail address: ytkang@khu.ac.kr (Y.T. Kang). 1 Present address: Institute of Advanced Material Study, Kyushu University, Kasuga-Koen 6-1, Fukouka 816-8580, Japan. 0360-5442/03/$ - see front matter  2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0360-5442(03)00064-1