On the characterization of sandwich panels for solar flat plate collectors’ applications: theoretical and experimental investigation

This paper presents an experimental characterization on the mechanical behaviour of four different sandwich panels, for use in thermal insulation. These Panels are the results of the combination of four composite materials; two materials as skins (Glass-Polyester and Plywood) and two as cores (Polystyrene and Cork agglomerate). From the comparison between the mechanical behaviour of these four sandwich panels which was tested for three point-bending tests; the sandwich with Glass-Polyester as skin and Cork agglomerate as core has the highest overall stiffness compared to the other sandwich panels. Furthermore, thermal characteristics of these four panels (insulation materials) were numerically used in a comparative study of thermal performances of solar flat plate collectors, FPCs. Thus, we have proceeded to the comparison of these FPCs efficiencies in order to determine the best performing model for agro-alimentary drying applications. From the comparison between these four FPCs, the highest efficiency was obtained from the FPC insulation panel with plywood as skin and cork agglomerate as core

Feasibility of solar adsorption air-conditioning in the region of Biskra: Reflection on the government support for electricity bills

In this paper, the feasibility of solar adsorption air conditioning system in the region of Biskra (Algeria) is studied. The main objective is to give a reflection on the current government support for electricity bills. A comparison between three air conditioning systems was made by taking into account economic and environmental constraints: classical mono-split system (A), classical centralized air conditioning chiller (B) and solar adsorption system (C). In the context of the current government support for electricity bills, results show that system A is actually the best choice from the total investment costs, electrical consumption and maintenance point of view. This is observed even with the gain of the electrical consumption obtained in the case of solar adsorption air conditioner (C). From an environmental point of view, the system (C) is more advantageous than the classical systems (A) & (B) especially for its use of the solar energy, its low electrical consumption, low CO2 emissions and low heat rejected to the outside. It can be concluded that the current state policy do not encourage the transition to the use of air conditioning systems operate by renewable energies. Thus, the redirection of the current support for electricity bills to the support of the investment cost of the solar adsorption air conditioner (C) will make it more competitive in the Algerian market. In this case, system (C) can replace, in the long-term, the system (A) used actually

Thermal design of air cooled condenser of a solar adsorption refrigerator

The objective of this paper is to study the design of a condenser of a solar adsorption refrigerator which will be tested in the region of Biskra (Algeria). The LMTD (log mean temperature difference) method is used to calculate the size of the condenser applying experimental data obtained from the literature. For this purpose, a calculation code has been developed to determine the total heat transfer area of the heat exchanger. Therefore, we present a comparison between calculated and experimental results obtained from the literature. This comparison allowed the validation of the calculation method by applying the same experimental conditions. The discussion of the results indicates that we cannot use the ambient air in free convection mode as a cooling fluid if its temperature exceeds 30°C. This problem presents the greatest obstacle especially in the Saharan regions, such as in Biskra, where the average ambient air temperature during the summer exceeds 35°C. As a solution, we propose in this article the improvement of the heat transfer by the air-forced convection mode. Thus, it is established that the use of the air fan can extend the operating temperature limits of the condenser above 35°C

Multiple solutions for flow mode−transition in an inclined cavity generated by natural convection

An investigation of natural convection in a rectangular cavity (AR = 4) filled with air (Pr = 0.71) heated from the side with adiabatic horizontal walls is carried out numerically. To describe the flow regime, we propose a description of the influence of the angle of inclination and Rayleigh number on the flow patterns likely to develop in this configuration. The numerical analysis of the governing equations of the problem is based on finite volume method with non-staggered grids arrangement and is solved through the iterative SIMPLEC algorithm. Results indicate that the angle of inclination has a significant effect on flow mode transition. The existence of multi-steady solutions closely depends on the value of the Rayleigh number. For that the Hysteresis phenomenon (multi−steady solutions) for Ra ≥ 2000 are demonstrated and parameter maps of Ra vs. φ are proposed

Applicability of solar desiccant cooling systems in Algerian Sahara: Experimental investigation of flat plate collectors

The increasing interest in the development of solar cooling technologies to their various economic and impressive environmental benefits, conducted us to study the feasibility of solar desiccant cooling systems in Algerian Sahara, particularly in the region of Biskra. Thus, we present in this paper, the results of an experimental investigation of solar flat plate collectors (FPCs) to test and estimate their heat regeneration capacity for solid desiccant cooling applications. The applicability of both Pennington and Dunkle cycles taking into account the effects of some parameters such as outdoor humidity and temperature and hot air temperature required to regenerate the desiccant wheel have been studied. From the psychrometric analysis, it was found that the Dunkle cycle is suitable in warm and semiarid climate. In addition, this study has allowed us to show that the temperature achieved by the flat plate solar air heaters in a large band of air flow rate can satisfy the energy needs for the dehumidification in desiccant cooling systems. Hot water produced by the solar water heaters and the stored one are in the operating temperature gap of the system (50-80 °C)

Contribution à l’étude des échanges convectifs en régime transitoire dans les Capteurs Solaires Plans à air ; Application au Séchage des produits agro-alimentaires

Solar air heaters can be used for many applications at low and moderate temperatures. There are different factors affecting the solar air heater efficiency, e.g. collector length, collector depth, type of absorber plate, glass cover plate, wind speed, etc. In this work we present an extensive comparative study on the thermal performance of various design of: single pass types of solar air heaters, SAHs: i) without obstacles, ii) with rectangular obstacles and iii) with a new form of obstacles (trapezoidal form) in the air flow duct. Thus, we have proceeded to the comparison of the best system with iiii) and double pass flat plate collector having the same type of obstacles in order to determine the best performing model. A theoretical model was constructed for all types of collectors, taking into account the new parameter, called the artificial roughness. Thus, we have proceeded to the application of these systems for the drying of agro alimentary products. We have sought to determine the drying kinetic for the forced convection. The drying air was heated by solar energy under variable outdoor conditions