Calorimetric measurements of the dynamics of a finned adsorbent: early assessment of the activated carbon cloth–ethanol pair with prismatic aluminium fins

Abstract

The heat of adsorption of the pair ethanol–activated carbon cloth (ACC) has been measured in a specialised calorimeter, following a step change in vapour pressure (the “large pressure jump”, LPJ) or a step change in temperature of the fin base (the “large temperature jump”, LTJ). This is the first time that LTJ has been attempted with this particular technique. The ACC was incorporated into a set of fins, representing small sections of finned tube adsorbent bed (~50 gram mass) and with a fin-to-fin gap of 6 mm. The heat rejection fitted an exponential decay, and for purposes of data fitting was adequately described by exponential decay, notwithstanding multiple physical effects within the ACC pack. Characteristic times, τ, were established for LPJ and LTJ. The characteristic times were adjusted to allow for sensible heat of the sample, making them indicative of change in refrigerant uptake and cooling power. For instance, for the LTJ 338 K→303 K, the characteristic time was 146 s without adjustment, but 183 s with adjustment. For the fins tested under LTJ, an “average” specific cooling power, defined with cycle time = 1.6 τ, was in the range of 0.36 to 0.52 kW kg−1, somewhat smaller than seen elsewhere and requiring future optimisation of the finned sample.