Parametric Study of to Design an Earth to Air Heat Exchanger with Experimental Validation

Geothermal energy uses an air ground exchanger to cool buildings with minimum of energy. The outlet air coming from this exchanger can be directly used for space cooling if its temperature is low enough. In this study we try to evaluate the profile of ground temperature to decide of the depth to bury the exchanger. Through modeling and experimentation, we try to evaluate the performance of a horizontal pipe used for cooling, for this finite differential method which consists on dividing the length of the exchanger on multiple equal segments and by the knowledge of initial and boundary conditions the profile of the air temperature is that carry out. The authors conclude that many parameters influence the performance of earth to air exchanger such as the nature of the ground, the ground depth diameter of the duct and the throughput flow

EMPIRICAL MODELS FOR LOSSES CALCULATION IN A RECTANGULAR DUCT EQUIPPED BY ARTIFICIAL ROUGHNESS

The objective of this work is to find empirical models linking load losses to the geometric characteristics of artificial roughnesscalled baffles and different modes of provisions of these fluids in the vein of a rectangular channel.An experimental design was set up to measure the losses Load caused by baffles between the upstream and downstream of thechannel. The experimental measurements made have enabled us to establish empirical relationships to evaluate losses inaccordance with load losses configuration and arrangement of baffles and for different flow regimes

EMPIRICAL MODELS FORLOSSES CALCULATION IN A RECTANGULAR DUCT EQUIPPED BYARTIFICIALROUGHNESS

The objective of this work is to find empirical models linking load losses to the geometric characteristics of artificial roughness called baffles and different modes of provisions of these fluids in the vein of a rectangular channel.An experimental design was set up to measure the lossesLoadcausedby baffles between the upstream and downstream of the channel. The experimental measurements made have enabled us to establish empirical relationships to evaluate losses in accordance with load losses configuration and arrangement of baffles and for different flow regimes

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

EFFECTS STUDY OF SOLID PROTUBERANCES PROPERTIES ON THE TURBULENT NATURAL CONVECTION PERFORMANCE INSIDE A VERTICAL CHANNEL

Dans cette étude, nous présentons des prédictions numériques des effets des propriétés géométriques, physiques et thermiques des protubérances, telles que la conductivité thermique des protubérances solides, les rapports d’aspect et les intensités du flux de chaleur exercées sur les faces externes des protubérances, sur la convection naturelle turbulente dans un canal vertical. Les résultats de l’analyse du transfert de chaleur sont obtenus en solutionnant les équations de l’écoulement de chaleur et des fluides en utilisant le modèle de la turbulence. Le système étudié est bidimensionnel, turbulent et permanant. La procédure numérique étend sur un code numérique qui modélise l’écoulement de chaleur et des fluides. Les résultats sont données en termes des champs et des profils des propriétés locales telles que la température, la vitesse, le coefficient de transfert de chaleur et l’intensité de la turbulence pour différents valeurs du rapport d’aspect des protubérances, la conductivité thermique et le flux de chaleur exercé sur les faces externes des protubérances. Les champs des propriétés d’air physiques et thermiques montrent des comportements différents en fonction de la valeur du rapport d’aspect des protubérances. Un effet positif sur le rendement de la convection naturelle turbulente a été prédit, dans la plage de 0 à 6,5%, par rapport à un canal vertical sans protubérances '. La présence des protubérances c’est un facteur important dans l’amélioration du rendement de la convection naturelle turbulente dans un canal vertical

Collector Efficiency by Single Pass of Solar Air Heaters with and without Using Fins

This paper presents the study of heat transfer in a solar air heater by using new design of solar collector. The collector efficiency in a single pass of solar air heater without, and with using fins attached under the absorbing plate has been investigated experimentally. Due to the adding the fins inferior an absorber plate, the desirable effect of increasing the heat transfer coefficient compensates for the undesirable effect of decreasing the driving force (temperature difference) of heat transfer, while the attached fins provide an enlarged heat transfer area. In this study, the absorbing plate of solar collector is attached with fins for further improved performance. The improvements of collector efficiencies in the single pass solar air heaters with, and without fins attached; increase with increasing the mass flow rate, especially for operating at lower air flow rate. Experiments were performed for two air mass flow rates of 0.012 and 0.016 kg/s. Moreover; the maximum efficiency obtained for the 0.012 and 0.016 kg/s with, and without fins were 40.02, 51.50% and 34.92, 43.94% respectively. A comparison of the results of the mass flow rates by solar collector with, and without fins shows a substantial enhancement in the thermal efficiency

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)

SIMULATION OF A SOLAR DRIVEN AIR CONDITIONING SYSTEM FOR A HOUSE IN DRY AND HOT CLIMATE OF ALGERIA

Solar cooling technology is environmentally friendly and contributes to a significant decrease of the CO2 emissions which cause the green house effect .Currently, most of the solar cooling systems commonly used are the hot water driven lithium bromide absorption chillers. According to the operating temperature of driving thermal source, single – effect Li Br/H2O absorption chillers have the advantage of being powered by ordinary flat-plate or evacuated tubular solar collectors available in the market. The main objective of this work is to develop a computational model that allows the simulation of an hourly basis for an absorption refrigeration - single - effect used the LiBr/H2O as solution working fluid- system assisted by solar energy and natural gas as auxiliary fuel coupled with the residential building located in the hot and dry climate of Algeria. This model will be developed using the dynamic simulation program TRNSYS, considering three specifics areas of work: determination of the cooling loads for a building, implementation of the computational model for the absorption refrigeration system and the parametric optimization of components, which will make possible an approach to optimal sizing of the solar absorption system. The results of the simulation of the absorption chiller indicate that an area of 28 m2 of flat plat collectors with an inclination of 35° and 800 L for hot storage tank provides an annual solar fraction of 80% and a thermal performance coefficient COP of 0.73, getting to cover demand of air conditioning in a house of 120 m2 located in Biskra (Algeria)

Effect of the Tilt Angle of Natural Convection in A Solar Collector with Internal Longitudinal Fins,”

Abstract-We present in this paper, a series of experimental tests carried out on a solar plan, with an area of 1.8236 m 2 capture, designed in the laboratory and tested in the region of Biskra. The complete experimental setup includes the measurement of global solar radiation, wind speed, airflow velocity and temperature and the ambient air at the inlet and outlet; optimize a tilt angle. The solar collector was oriented facing south Renewable and domestic energy source, and is essential components of a sustainable energy future. This paper deals with the influence of the tilt angle of solar collectors. The optimum angle is measured by searching for the values for which the total radiation on the collector surface is a maximum for a particular day or a specific period. An application of the model is done using the experimental data measured for Biskra in Algeria. For increasing the utilization efficiency of solar collectors, it is recommended that, if it is possible, the solar collector should be mounted at the monthly average tilt angle, and the slope adjusted once a month