Compressor driven metal hydride cooling systems—mathematical model and operating characteristics Sagnik Mazumdar, Souvik Bhattacharyya * , Maddali Ramgopal Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur 721302, India Received 22 December 2003; received in revised form 3 January 2005; accepted 28 February 2005 Available online 17 May 2005 Abstract A detailed mathematical model of a compressor driven metal hydride (CDMH) cooling system is presented. The model takes into account the transient characteristics of the coupled metal hydride reactors with external fins, reciprocating compressor and conditioned space. The model can be used for predicting the system performance during the initial pull-down as well as the stable cycling periods. Results are obtained for a 1 kW capacity air conditioning system using optimized reactors packed with Zr 0.9 Ti 0.1 Cr 0.55 Fe 1.45 hydride. The COP’s obtained are in the range of 1.7–2.2 depending on operating conditions while the specific cooling power obtained is about 600 kJ kg alloy K1 h K1 . It is shown that in order to make these systems commercially viable it is important to select suitable materials with fast reaction kinetics. Since, system performance parameters can be predicted more effectively, the model can be used for design of optimized systems. q 2005 Elsevier Ltd and IIR. All rights reserved. Keywords: Air conditioning; Reciprocating compressor; Absorption system; Metal hydride; Modelling; Performance; COP; Transient Syste `mes de refroidissement pour compresseurs a ` hydrure me ´tallique — mode `le mathe ´matique et caracte ´ristiques de fonctionnement Mots cle ´s : Conditionnement d’air ; Compresseur a ` piston ; Syste `me a ` absorption ; Hydrure me ´tallique ; Mode ´lisation ; Performance ; COP ; Regime transitoire 1. Introduction Environmental concerns in recent years have led to the current interest in systems based on natural refrigerants such as carbon dioxide, water, hydrogen, etc. Studies on novel hydrogen based metal hydride systems is a step in this direction. Several theoretical and experimental studies reported on heat operated metal hydride cooling and heating systems [1–6] show that even though these systems offer the advantage of using low grade sources of energy, they suffer from disadvantages such as low COPs and high life-cycle costs compared to vapour compression refrigeration systems (VCRS). Compared to the heat operated systems, the International Journal of Refrigeration 28 (2005) 798–809 www.elsevier.com/locate/ijrefrig 0140-7007/$35.00 q 2005 Elsevier Ltd and IIR. All rights reserved. doi:10.1016/j.ijrefrig.2005.02.002 * Corresponding author. Tel.: C91 3222 282904; fax: C91 3222 255303. E-mail address: souvik@mech.iitkgp.ernet.in (S. Bhattacharyya).