Optimization of the distance between the rows in solar collectors’ arrays

The article presents some results of the analysis of the influence of the distance between the collectors’ rows in thermal solar systems on the degree of self-shading. For the purposes of the study, the dimensionless ratio Ks between the required minimum distance between the rows, guaranteeing the absence of self-shading, and the height of the collectors, was used. A simulation study was performed for specific climatic conditions and the annual solar radiation incident on the collectors’ array at different degrees of self-shading was determined. Its annual financial equivalent for various alternative heat sources (electricity, natural gas, wood pellets, district heating and gas oil) was assessed, as well as the necessary investment costs for construction of the solar system. A regression relationship between the coefficient of net present value NPVQ and Ks was derived and its optimal values were established, which ensure the achievement of maximum economic efficiency of the system operation for the considered replaced heat sources

Assessment of the annual performance of solar collectors by means of the utilizability method

This report presents some results from a comparative analysis of the long-term efficiency of flat-plate and evacuated tube solar collectors under different operating conditions. The analysis involves calculation of the daily utilizibility factor, which is defined as the fraction of total monthly solar radiation over an inclined surface that exceeds the critical value. The monthly values of the critical radiation and the daily utilizability factor for the solar collectors are determined under different climatic conditions and different temperatures of the heat transfer fluid. The obtained results are used to compare the annual performance of the solar collectors

Analysis of the efficiency of an embedded floor heating for snow melting and freeze protection

An algorithm for modelling and numerical simulation of the three dimensional conjugate heat transfer in slab-embedded snow melting and freeze protecting systems is developed. The influence of the climate conditions on the heat transfer in the constructions is modelled according to the correspondent design method of ASHRAE. The models are verified and solved numerically via finite volume method for a road embedded hydronic installation at different piping configurations. The fluid flow parameters and temperature fields in the construction are obtained at steady state climate conditions, hardest for 95 % of the wintertime for the region. An analysis of the efficiency of the modelled configurations is implemented based on the computed snow-free area ratio of the road surfaces

An experimental study for drying Pisum sativum on an electric dryer and a heat pump dryer

A study of drying parameters on the drying process of Pisum Sativum bean was carried out. The effects of drying temperature of moisture air from 40°C to 80°C on the drying time and on the drying kinetics were demonstrated not only on conventional electric dryers but also on heat pump dryers. Besides, checking the steady operation of the heat pump dryer was also considered. The results show that, when temperature rises, the shorter time and the faster removal of moisture content can be obtained for both dryer systems. Drying in an electric heater at 80°C took only 1 hour 45 minutes, but the broken skin of pea seeds happened. The comparison of heat pump dryer and electric dryer was presented with the shorter drying time on heat pump than electric dryer as a result of removing water vapor from moisture air at the evaporator of heat pump, it led to the reduction of specific humidity of air entering the drying chamber. And the last impressive result which can be seen is that the drying rate of a heat pump is higher than an electric dryer at the same drying temperatures beside the energy consumption of electric dryer is 2.76 times as much as that of heat pump dryer