RP-Department of Energy Engineering

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Browsing RP-Department of Energy Engineering by Author "Li, T.X."

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    A combined doubleway chemisorption refrigeration cycle based on adsorption and resorption processes
    (2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.
    An innovative combined double-way chemisorption refrigeration cycle based on adsorption and resorption processes is presented. Two different reactive salts were used as sorbents and ammonia was utilized as the refrigerant in the proposed cycle. The useful cold was obtained from the evaporation heat of the refrigerant during the adsorption process and from the reaction heat of the low-temperature salt during the resorption process. The proposed combined double-way cycle has a distinct advantage of higher coefficient of performance (COP) in comparison with conventional adsorption cycle or resorption cycle. Experimental verification indicated that the advanced combined double-way cycle is feasible for refrigeration application, and the ideal COP of the basic cycle was about 1.24. Theoretical results showed that the proposed combined double-way cycle could improve COP by 167% and 60% when compared with conventional adsorption cycle and resorption cycle, respectively.
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    Lithium Chloride–Expanded Graphite Composite Sorbent for Solar Powered Ice Make
    (2010) Kiplagat, J.K.; Wang, R.Z.; Oliveira, R.G.; Li, T.X.
    Consolidated composite material made from expanded graphite (EG) powder impregnated with LiCl salt is proposed for use in solar powered adsorption ice makers. Laboratory experiments were done to test the adsorption and desorption performance of the sorbent under different temperature conditions suitable for solar energy utilization. More than 75% of the reaction between LiCl and ammonia was completed after 30 min of synthesis at evaporation temperatures of −10 and −5°C and adsorption temperature between 25 and 35°C. Under the same period, it was possible to obtain 80% conversion in the desorption phase, when the generation temperatures ranged between 75 and 80°C, and the condensation temperature varied from 25 to 35°C. The highest average specific cooling power during the synthesis phase was 117 W per kg of the block. The calculated theoretical coefficient of performance (COP) under different cycle conditions was nearly constant at 0.47. Moreover, the new composite sorbent showed higher Specific Cooling Capacity (SCC), compared to activated carbon (AC)/methanol pair. Experiments done with blocks with different proportion of EG, showed that the proportion of EG influence the cooling capacity per unit mass of salt and had almost no influence on the cooling capacity per unit mass of the block. Moreover, the reaction enthalpy (ΔH) and entropy (ΔS) were calculated from experimental data obtained experimentally, and confirmed previous reported
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    Performance study of a consolidated manganese chloride-expanded graphite compound for sorption deep freezing processes
    (2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.
    A consolidated composite sorbent made from manganese chloride and expanded graphite was produced for sorption deep-freezing processes and used for cold production at a temperature as low as −35 °C. Experimental results showed that the addition of a porous graphite matrix can prevent the agglomeration and the attenuation of sorption capacity of reactive salt. The composite sorbent could incorporate 0.537 kg of ammonia per kg of reactive salt and the average specific cooling power (SCP) obtained varied between 200 W kg−1 and 700 W kg−1 when the evaporation temperature ranged from −35 °C to 0 °C. The analysis of the data suggested that the heat transfer characteristic in the composite sorbent was strongly influenced by chemical reaction and the conversion rate was very sensitive to the constraint temperatures. The SCP and coefficient of performance (COP) of a simple sorption deep-freezing system were 350 W kg−1 and 0.34, respectively, at the generation temperature of 180 °C, the heat sink temperature of 25 °C and the evaporation temperature of −30 °C.
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    Thermodynamic study of a combined double-way solid–gas thermochemical sorption refrigeration cycle
    (2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.
    A combined double-way thermochemical sorption refrigeration thermodynamic cycle was proposed and tested. Both adsorption refrigeration and resorption refrigeration processes were combined in order to improve the system performance. Two different consolidated composite materials were used as the reactive sorbents and ammonia was used as the refrigerant. Experimental results showed that a system operating with such proposed cycle can have two useful cold productions during one cycle at the expense of only one heat input at high temperature. The average specific cooling power (SCP) during the adsorption refrigeration phase was 301 W kg−1. Analysis of the experimental data showed that the driving equilibrium drop during the resorption process was much lower than that during the adsorption process, when the cold production temperature was similar. The proposed combined double-way sorption cycle has a larger cooling capacity per unit of heat input and the maximum theoretical coefficient of performance (COP) is 1.24 when MnCl2 and BaCl2 are used as the reactive sorbents.