Internal irreversibilities’ influence on the new thermo-ecological criterion for real absorption refrigerators

Irreversibility is classified in two main types: internal and external irreversibilities. Internal irreversibility is due to turbulence, pressure gradients, mixing and diffusion processes within the system, which is represented by two irreversibility parameters indicating the deviation from an endoreversible case. This paper studies and analyses the effects of two internal irreversibility parameters (the internal irreversibility parameter for generator–absorber assembly and the internal irreversibility parameter for condenser–evaporator assembly) on the optimal ecological performances of an irreversible four-heat-source absorption refrigerator based on the ecological coefficient of performance (ECOP) criterion. The ECOP objective function is defined as the ratio of the cooling load to the loss rate of availability (or entropy generation rate). The results obtained show that the internal irreversibility parameter for condenser–evaporator assembly affects more the ecological performance of the system than the internal irreversibility parameter for generator–absorber assembly. This is of importance to the optimal design and performance improvement of absorption refrigeration cycles.     

Solar energy absorption by acrylic coatings—II: the effect of alternating environmental conditions

Atmospheric corrosion of building materials is an enormously complex and interdisciplinary process. It affects not only the ability of building to perform over the prolonged period of time but also the overall energy consumption. The presented paper is a part of a larger study on application of acrylic plasters in passive solar systems. Absorption characteristics as well as microstructural features of acrylic plasters subjected to alternating climatic conditions have been analysed. In order to simulate the real conditions, samples were exposed to the variations of temperature and humidity, near-daylight radiation (xenon lamp) and subjected to acid and alkaline environments.     

Analysis of a combined photovoltaic–geothermal gas-fired absorption heat pump system in a Canadian climate

This study examines the technical feasibility of using a geothermal gas-fired absorption heat pump (A-GSHP) for space conditioning and domestic hot water heating in a Canadian climate. The A-GSHP is coupled to a photovoltaic (PV) system with battery storage intended to ensure the full autonomy of the heating, ventilating and air conditioning (HVAC) system from the electric grid. The system is modelled using TRNSYS with standard models and a new performance-based A-GSHP model, which accounts for part-load operation. Results indicate that the coefficient of performance (COP) is equal to 1.12, 0.55 and 1.79 for heating only, cooling only and simultaneous cooling and domestic hot water (DHW) heating, respectively. A 13.5 kWp PV array and a 400 kWh battery storage are necessary to provide the electrical power required to operate the A-GSHP and the associated HVAC system at all times without importing electrical energy from the grid.     

Enhancing the efficiency of absorption refrigeration cycle by ‘seeding’ nanoparticles directly in the working fluid

The fossil fuel-driven electricity grid supplies space cooling especially in tropical/temperate climate regions. The timing of the peak load closely coincides with the peak of available solar irradiance. Therefore, solar-driven space cooling can reduce the peak loads in a smart grid. Solar-powered, direct absorption refrigeration cycles fit well. The efficiency of this cycle can be enhanced through the use of new, engineered materials. This study analyses a model of ammonia–water based absorption refrigeration cycle in which nanoparticles are directly ‘seeded’ in the working fluid itself. The model has been tested at various locations in India.     

Mixture design concept and mechanical characteristics of PS ash–cement-treated clay based on the water absorption and retention performance of PS ash

In an attempt to reduce environmental impact, paper sludge ash (PS ash) has recently been studied for its complementary reuse with cement for soil stabilization. In order to establish the optimal mixture design for combining PS ash and cement in soils, a detailed investigation into the stabilizing mechanism is required. To assess the combined effects of PS ash and cement on the strength development of stabilized clay soil, referred to as PS ash–cement-treated clay, a new critical parameter, the unabsorbed and unretained clay-water/cement ratio W*/C, was proposed. To determine W*/C, a new testing method for evaluating the water absorption and retention performance of PS ash was developed. It was revealed that the water absorption and retention rate W_ab of PS ash increased with curing time. Unconfined compression tests conducted on the PS ash–cement-treated clay with various water-cement–PS ash mixture proportions and different curing times affirmed that the strength development was fundamentally governed by the parameter W*/C. This suggests that the water absorption and retention rate W_ab obtained by the developed method is an essential material parameter in the mixture design for the PS ash–cement-treated clay. It was also found that the effect of the hybrid treatment method, which uses both cement and PS ash, was better than that of the method which uses cement alone, particularly under high W*/C conditions. This indicates that the water absorption and retention performance of PS ash can be fully utilized when the mixture has sufficient unabsorbed and unretained water for cement hydration.