Carbon 40 (2002) 2855–2859 Effect of packing density and adsorption parameters on the throughput of a thermal compressor a,b a b b, * B.S. Akkimaradi , M. Prasad , P. Dutta , K. Srinivasan a Thermal Systems Group, ISRO Satellite Centre, Bangalore 560017, India b Department of Mechanical Engineering, Indian Institute of Science, Bangalore 560012, India Received 6 April 2002; accepted 19 June 2002 Abstract Vapour adsorption refrigeration systems (VAdS) have the advantage of scalability over a wide range of capacities ranging from a few watts to several kilowatts. In the first instance, the design of a system requires the characteristics of the adsorbate–adsorbent pair. Invariably, the void volume in the adsorbent reduces the throughput of the thermal compressor in a manner similar to the clearance volume in a reciprocating compressor. This paper presents a study of the activated carbon 1HFC-134a (1,1,1,2-tetrafluoroethane) system as a possible pair for a typical refrigeration application. The aim of this study is to unfold the nexus between the adsorption parameters, achievable packing densities of charcoal and throughput of a thermal compressor. It is shown that for a thermal compressor, the adsorbent should not only have a high surface area, but should also be able to provide a high packing density. Given the adsorption characteristics of an adsorbent–adsorbate pair and the operating conditions, this paper discloses a method for the calculation of the minimum packing density necessary for an effective throughput of a thermal compressor.  2002 Elsevier Science Ltd. All rights reserved. Keywords: A. Activated carbon; C. Adsorption; D. Density 1. Introduction equilibrium point. The objective of this paper is to bring out the strong link between the adsorption and thermo- The first step to the development of VAdS is the dynamic characteristics of the adsorbent1adsorbate pair characterisation of the adsorbent1adsorbate pair from an and the packing density realisable in practice. This is adsorption point of view. This involves the experimental achieved by using the adsorption isotherms for activated determination of the amounts adsorbed as a function of carbon 1HFC134a generated over a temperature range of pressure at constant temperatures and the deduction of the 273–353 K and a pressure range up to 0.65 MPa using a heats of adsorption and a number of adsorption parameters. volumetric method [1]. The adsorption parameters enable the derivation of a mathematical relation between the specific adsorption (the quantity of adsorbate adsorbed per unit mass of adsorbent), 2. Materials and methods pressure and temperature. The adsorption parameters also allow the calculation of isosteric heats of adsorption and A detailed description of the experimental techniques is the determination of the maximum possible throughput of given in Ref. [1], an abstract of which is provided the adsorption thermal compressor for a given set of hereunder for the sake of completeness. The specimens of operating conditions. Yet, a practical thermal compressor is charcoal studied are listed in Table 1. For Fluka specimen seldom able to generate this level of throughput because of the carbon content was found to be 98.77%, the particle the presence of void volume and operation away from the size ranged from 2 to 65 mm with a mean of 21.6 mm and the BET surface area obtained from 77 K nitrogen 2 21 adsorption isotherm was 1143 m g [2]. Chemviron *Corresponding author. Tel.: 191-80-394-2589; fax: 191-80- specimen had the same nitrogen adsorption parameter, a, 360-0648. E-mail address: mecks@mecheng.iisc.ernet.in (K. Srinivasan). in the Dubinin’s adsorption equation [3] as the Sarabhai 0008-6223 / 02 / $ – see front matter  2002 Elsevier Science Ltd. All rights reserved. PII: S0008-6223(02)00218-X