Effect of packing density and adsorption parameters on the throughput of a thermal compressor

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 +HFC-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. (C) 2002 Elsevier Science Ltd. All rights reserved

Adsorption of nitrogen on activated carbon-refit of experimental data and derivation of properties required for design of equipment

10.1021/je900236pJournal of Chemical and Engineering Data5482291-2295JCEA

Adsorption of 1,1,1,2-Tetrafluoroethane on Activated Charcoal

This paper presents adsorption isotherms for HFC-134a on activated charcoal, in the temperature range of 273-353 K and for pressures up to 0.65 MPa, measured using the volumetric method. Three samples of charcoals with widely varying surface areas were chosen. The shapes of the isotherms,obtained from the experimental data were similar in all cases and comparable to those reported in the literature. Adsorption parameters were evaluated from the isotherms using the Dubinin-Astakhov (DA) equation. The concentration dependence of the isosteric enthalpies of adsorption is extracted from the data

Numerical and Experimental Studies of Parasitic Heat Losses in Coldfinger of a Pulse Tube Cryocooler in Off-State Condition

A pulse tube cryocooler (PTC) for future metrological satellites has been developed at one of the lead centers of the Indian Space Research Organisation in Bangalore, India for cooling on-board Infrared (IR) detectors to 80 K.A study has been conducted on the coldfinger of PTC to understand the off-state heat loads on the cooler by varying the value of gravity numerically in ANSYS FLUENT and experimentally by orienting the setup with respect to gravity. The off-state parasitic losses represent a major heat load in on-board applications that include redundant, viz. nonoperating coolers. To find out the amount of off-state parasitic heat losses in a nonoperating coldfinger of the PTC experimentally, transient warm-up technique was used. Various heat loads were applied experimentally on the cryo-tip at temperatures ranging from 80 to 100 K for determining the parasitic losses. The effect of orientation of PTC on the off-state parasitic heat load with respect to gravity is studied and presented in this paper. Enhancement due to free convection heat flow normalized by gas molecular conduction in pulse tube is analyzed using computational fluid dynamics to verify and compare with experimental results. The best orientation angle where the parasitic is low is when the cold end of the coldfinger of pulse tube cryocooler faces down (0A degrees) and high when the cold end of the coldfinger is oriented to 135A degrees

Adsorption Characteristics of The Charcoal-Nitrogen System at 79-320 K And Pressures To 5 MPa

Adsorption isotherms are obtained for the charcoal-nitrogen system in the temperature range 79-320 K and pressures to 5 MPa for two samples of activated charcoal. Correlations relating temperature dependence of adsorption potential are obtained using four methods of extrapolating pseudo-saturation state beyond the critical point. The values obtained are compared with literature data. Using the experimental results and the BET theory surface area and micropore volume are calculated. It is brought out that samples of activated charcoal need to be characterized prior to their use in the design of low temperature adsorption based cryorefigeration system

Development of a laboratory model of activated charcoal-nitrogen adsorption cryocooler

The development of a laboratory model of a charcoal-nitrogen adsorption cryocooler is described. The results on characterization of various components of this cooler and performance of the ensemble are presented. Four compressor cells are operated 90° out of phase to generate 0.0364 g/s (1.75 slpm) of nitrogen at a pressure of 5.2 MPa. The cycle time per compressor was 8 min, equally apportioned between heating and cooling. The high pressure gas is pre-cooled to 193 K and expanded through a J-T/heat exchanger assembly. A cold tip temperature of 124 K is obtained at a parasitic heat load of 0.36 W