Novel compact sorption generators for car air conditioning

A prototype compact generator using the activated carbon-ammonia pair based on the plate heat exchanger concept has been designed and built at Warwick University. The novel generator has low thermal mass and good heat transfer. The heat exchanger uses nickel-brazed shims and spacers to create adsorbent layers only 4 mm thick between pairs of liquid flow channels of very low thermal mass. The prototype sorption generator manufactured was evaluated under EU car air conditioning test conditions. The prototype sorption generator is described and its experimental performance reported. While driven with waste heat from the engine coolant water (at 90 degrees C), a pair of the current prototype generators (loaded with about 1 kg of activated carbon) operating out of phase has produced an average cooling power 1.6 kW with about 2 kW peaks. The typical average COP obtained is 0.22

Feasibility study of ground source solar driven adsorption heat pump

The feasibility study of a ground source-solar driven adsorption heat pump and air conditioning system for potential use in UK (Reference city: London Gatwick) is based on fully described layout. The system is initially specified to operate as air conditioning machine with a maximum cooling capacity of 3 kW and a maximum heating capacity of 7 kW. The weather data from METEONORM are used to evaluate the system performance. The Evacuated Tube Solar Collector is sized for a surface area of 15.2 m2 (estimated capital of about €11,100) based on the hottest day of the year (19 August). The key performance indicators, namely the maximum cooling power and the COP (Coefficient of Performance) were about 2.7 kW and 0.47 respectively at midday with an ambient temperature of 27.1oC

Application of a compact sorption generator to solar refrigeration: case study of Dakar (Senegal)

The feasibility of applying a low cost plate heat exchanger solid sorption reactor to solar powered refrigeration is investigated by using a validated reactor model. The proposed system is targeted at ice-making in developing countries for food preservation. The adsorption refrigeration machine modelled employs the active carbon-ammonia working pair in both two-bed and four-bed regenerative systems. Driving heat is provided from standard flat plate and evacuated tube solar collectors. The capital cost of a one-off machine with four regenerative beds which could produce up to 1000 kg of ice per day in Dakar (Senegal) is estimated at €68,000

Anisotropic thermal conductivity and permeability of compacted expanded natural graphite

The anisotropic thermal conductivities and permeabilities are investigated for discs and plates of compacted expanded natural graphite. The measuring directions of heat conductivity and permeability are both parallel and perpendicular to the pressing direction of compacted samples. An unexpected phenomenon is found in that the thermal conductivity sometimes decreases as the density of the material increases, and this phenomenon only occurs for thermal conduction parallel to the compressing direction. The results also indicate that the direction perpendicular to the compression direction shows higher thermal conductive properties and permeability values. Both anisotropic thermal conductivities and permeabilities are strongly dependent on density. Analysis shows that as a type of porous material, the ENG yields layers under the effect of pressure, and their orientation influences the values of heat conductivity and permeability of the different samples

http://wrap.warwick.ac.uk/ Effect of packing density on thermal properties of granular activated carbon packed bed by using of inverse heat conduction method

Original citation: Khaliji Oskouei, M. and Tamainot-Telto, Zacharie (2014) Effect of packing density on thermal properties of granular activated carbon packed bed by using of inverse heat conduction method. Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions: The version presented in WRAP is the published version or, version of record, and may be cited as it appears here. ABSTRACT The ability of granular activated carbon (GAC) to adsorb large mass of refrigerant gases makes it ideal for use in thermal compressor. In order to make thermal compressor economically viable, the size must be reduced and for that reason thermal responses should be increase as much as possible during heating and cooling process. This paper investigates the effect of GAC bed density on the thermal transient responses when a sudden change in temperature is imposed on wall of a test sample reactor

Isothermal sorption characteristics of the BaCl2-NH3 pair in a vermiculite host matrix

Chernisorption could be useful in adsorption systems due to the large concentration change compared with physisorption. Equilibrium concentration characteristics of ammonia with a composite adsorbent material (BaCl2 impregnated into a vermiculite matrix) are investigated: the maximum concentration is about 0.4 kg ammonia/kg adsorbent. Hysteresis was observed between the synthesis and the decomposition reactions. The analysis of the data suggests that the hysteresis could be due to the dimensional changes of the solid during the reactions. The bi-variant behaviour observed was contrary to the mono-variant behaviour anticipated and the reasons are discussed. The COP of a basic adsorption cycle for typical ice-making and air-conditioning applications utilizing ammonia and the composite material were calculated. The results show that the material could be used for air-conditioning or other refrigeration applications. The COP could reach up to 0.6 at typical conditions (T-cv = 15 degrees C, T-con = 35 degrees C)

Thermal conductivity and permeability of consolidated expanded natural graphite treated with sulphuric acid

The thermal conductivity and permeability of consolidated expanded natural graphite treated with sulphuric acid (ENG-TSA) were measured both parallel and perpendicular to the direction of compression used to produce the samples. Results showed that the thermal conductivity and permeability were highly anisotropic. The thermal conductivity perpendicular to the direction of compression was 50 times higher than that parallel to the direction of compression and the permeability was 200 times higher. The maximum thermal conductivity measured was 337 W m(-1)K(-1) at a bulk density of 831 kg m(-3). The permeability perpendicular to the direction of compression varied in the range of 10(-11) to 10(-16) m(2) as the density increased from 111 to 539 kg m(-3). The specific heat was measured, and the average value is 0.89 kJ kg(-1) K(-1) in the temperature range 30-150 degrees C. As a type of heat transfer matrix the thermal diffusivity was about five times higher than that of, for example, pure aluminium due to the combination of improved thermal conductivity with comparatively low density and reasonable specific heat. (C) 2011 Elsevier Ltd. All rights reserved

Study of thermal conductivity, permeability, and adsorption performance of consolidated composite activated carbon adsorbent for refrigeration

Composite adsorbents, comprising activated carbon and expanded natural graphite, have been developed, and their thermal conductivity, permeability and adsorption performance were tested. The thermal conductivity varied with the ratio of activated carbon to expanded natural graphite. Thermal conductivity increased as the ratio of expanded graphite increased. Considering that the density of activated carbon for the composite adsorbent should not be lower than 200 kg/m(3), otherwise the volumetric cooling capacity would be unacceptably low, the highest thermal conductivity obtained from experiments was 2.47 W m(-1) K(-1). The permeability was also measured, and the best result obtained was 4.378 x 10(-12) m(2). In order to evaluate the influence of heat and mass transfer on adsorption performance, the adsorption rate was tested using a Rubotherm magnetic suspension balance, and results showed that for the freezing conditions lower than -10 degrees C the performance of granular activated carbon was better than that of solidified adsorbent because of the reduced mass transfer of ammonia at low saturated pressure. The adsorption performance of consolidated adsorbents increased rapidly when the evaporating temperature was higher than -10 degrees C. When the evaporating temperature was 8 degrees C, the adsorption rate of consolidated adsorbent was improved by 29% if compared with that of granular adsorbent. (C) 2011 Elsevier Ltd. All rights reserved