• Energy Research

Abstract Thermally driven cooling systems are becoming increasingly important as an alternative to the conventional mechanical vapour compression cooling systems. Among these technologies, thermochemical cooling offers a large number of chemical reactions in a wide range of operating conditions, which can use low-grade waste heat, as well as solar, biomass or geothermal energy resources. In this work, an intermittent prototype of a single stage thermochemical cooling system, using the reaction: barium chloride and ammonia (BaCl2, 8NH3) was designed, constructed and evaluated. In this work industrial grade reagents were utilized without additive compounds to improve the heat transfer. The pressure-temperature equilibrium was similar to that reported in the literature. The generation temperatures ranged between 54 and 69 °C where up to 6.65 L of liquid ammonia was desorbed. Anhydrous BaCl2 was obtained from dehydration of di-hydrate-BaCl2, which it was carried out into the reactor, in order to evaluate the feasibility of these operations under actual conditions. The thermochemical reaction rate in general depended on the working temperatures and constant pressure; in this work the evaporator temperatures ranged from 2 to 5 °C at absorber temperature at 32 °C. Preliminary results show the feasibility of operating the thermochemical cooling cycle with low temperature sources, with almost constant operating conditions using industrial grade reagents.

Abstract This paper proposes an accurate estimation for the experimental thermodynamic performance of a Single Stage Absorption Heat Transformer (SSHT). The calculation includes five heat and mass transfer effectiveness factors of the components in the SSHT. The evaporator, condenser and heat exchanger effectiveness is based on the method of Number of transfer units (NTU). Absorber and generator effectiveness are correlated with mass transfer, concentrations of the working mixture, and external powers, respectively. Calculations according to the operating conditions of the experimental tests were carried out in a 4 kW absorption heat transformer. The experiment was performed with the water/Carrol mixture with concentrations from 66 to 69%w; the actual Coefficient of Performance (COP a ) values were from 0.28 to 0.35, while the classical model overestimates these values from 0.47 to 0.49, respectively. The predicted COPη with these effectiveness factors is much more accurate (error factor lower than 92.25%) with COP a .

Abstract This paper reports on the experimental results of a double-absorption heat transformer operating with a H2O/LiBr mixture. The generator and evaporator are pool boiling type heat exchangers, while the remaining components are coils inside shells. Plots of gross temperature lifts, economizer efficiency, and internal and external performance coefficients are reported as functions of diverse operating parameters of the heat transformer. The results indicate that the system can achieve gross temperature lifts (GTLs) of between 48 °C and 74 °C, with internal performance coefficients varying from 0.12 to 0.37. The GTLs achieved are up to 30 °C higher than those reported in the literature, using a single-stage heat transformer operating with the same working mixture. Furthermore, the system exhibits effective stability and repeatability.