B.A. Jubran

Convective heat transfer and pressure drop characteristics of various array configurations to simulate the cooling of electronic modules

Abstract This paper reports an experimental investigation to explore the effects of the size of modules, the presence of a cylindrical module and the missing module on the heat transfer coefficient and pressure drop characteristics of array configurations composed of individual rectangular modules for three different Reynolds numbers namely; 1690, 2250 and 2625. Generally, it was found that using different sizes or shapes of modules in an array configuration tends to increase the Nusselt number by as much as 40% for the rectangular module and 28% for the cylindrical module. The presence of a missing module in the array resulted in a 37% enhancement in the Nusselt number downstream the missing module. Pressure drop results indicate that large size modules tend to enhance the pressure drop at their row locations by as much as 15%, while the cylindrical module tends to attenuate the pressure drop especially at low Reynolds number.

COMPARISON OF DIFFERENT TWO-EQUATION TURBULENCE MODELS FOR PREDICTION OF FILM COOLING FROM TWO ROWS OF HOLES

The present investigation involves the prediction of film cooling from two rows of holes using different turbulence models. Predictions of film cooling effectiveness and the velocity field from two rows of holes inclined in the streamwise direction are presented using the k-ω model and a modified version of it, as well as the standard k-e model together with its nonisotropic version. Comparison between the predicted results using these models and previous experimental results indicates that the ability of a turbulence model to prediet the experimental results depends heavily on the blowing rate as well as on the distance downstream from the injection holes.

Modeling and simulation of solar pond floor heating system

This paper presents the development of modeling, simulation and analysis of a solar pond floor heating system. The developed computer simulation has been used to study the potential of using such a system under climatic conditions in Jordan. It was found that the solar pond heating system could meet most of the winter season in Jordan with Solar fraction in the range 80–100% for at least 2 months of the season. It must be emphasized that the feasibility of such a system is its utilization in district heating and not for individual households due to the limiting economical factors of high capital cost of the solar pond for small domestic applications.

Optimization of solar pond electrical power generation system

This paper investigates the potential of using a solar pond for the generation of electricity in Jordan. A solar pond power plant model is presented to simulate and optimize such a system under the Jordanian climatic conditions. A Rankine cycle analysis is carried out using an environmentally friendly working fluid, Refrigerant 134a. It was found that using a solar pond for the generation of electricity in Jordan has the potential, with the cost of 0.234 JD/kWh when using a pond of surface area of 1.5 km2, to generate 5 MWe.

Parametric study of a box-type solar cooker

Abstract This paper presents the theoretical analysis and performance investigation of a single, as well as double, glazed box-type solar cooker with or without reflectors. The mathematical model is developed using the heat balance analysis of the various components of the cooker. In the present analysis, the properties of cooking materials and the value of the overall heat loss coefficient are allowed to vary as a function of the absorber plate and food temperatures. The obtained thermal equations are solved on the computer using a stepwise solution which enabled the temperatures of the various elements of the cooker to be predicted. An optimization parametric study has been performed using several important parameters of the cooker. The effect of those parameters on the cooker performance was studied. The results of the theoretical investigation are compared with the experimental results available. The experimental results conform reasonably with the predicted values.

Development and testing of concrete solar collectors

This paper investigates the development and performance of three types of concrete solar collectors made from locally available materials. The only difference between these collectors was the flow passage materials. These passages were made from locally manufactured Galvanized Steel Pipes (GSP). Propyleneglycol (Thermopipe) and Polyvinyl Chloride (PVC) pipes. It was found that concrete solar collector with galvanized steel pipes was as good as local metallic conventional collectors with a daily efficiency as high as 40% compared with 45% for the local metallic conventional one. The time constants for concrete collectors investigated are much higher than metallic collectors, with the value as high as 37.4 minutes.

Numerical model for the behaviour of a salt-gradient solar-pond greenhouse-heating system

This paper reports a parametric study of a salt-gradient solar-pond greenhouse-heating system under Jordanian climatic conditions, using a one-dimensional numerical model which has been solved using a definite difference technique. The model makes use of several empirical correlations for calculating solar fluxes, and heat losses from the solar pond. The parameters considered include the surface area of the pond, the non-convective zone (NCZ) and the lower convective-zone (LCZ) thicknesses, the inclination wall angles of the pond, the greenhouse area, the greenhouse cover transmittance, and the thermal load extracted. It has been found that, under Jordanian climatic conditions, the solar pond can provide 30% of the heating load for the greenhouse.

Solar hybrid heating systems for greenhouses

Theoretical prediction of the total heat requirements of a greenhouse using several solar hybrid systems under various representative Jordanian ambient conditions have been carried out. Either an air-source heat pump, a water-source heat pump, a boiler, and electric-resistance element system or a combination of these was considered as the heat source. The operation-cost analysis which was carried out indicated that for the given ambient conditions the hybrid solar heat-pump system was in general the most economic.

Computational evaluation of solar heating systems using concrete solar collectors

Abstract This paper uses the F -chart technique to evaluate three types of solar heating systems, namely; space solar heating and domestic hot water system (SHDHW), domestic hot water system (DHW) and solar swimming pool heating system (SPHS), using three types of concrete solar collectors, models A, B, and C, and one conventional metallic solar collector. The economical analysis of SHDHW system revealed that the concrete collectors provided about 49 and 63% of the annual load when the collecting area of the solar panel increased from 55 to 88 M 2 (25 to 40% of the building roof area). The corresponding solar contributions when conventional metallic collectors were used are 41 and 53%, respectively. This represents an improvement of the annual solar fraction of about 19% when concrete collectors are used instead of the metallic collectors. It was found that solar heating systems with concrete solar collector models gave higher solar fractions and total life cycle savings than the conventional solar metallic collector.

Modelling free convection in a trombe wall

In this paper, the convective laminar heat transfer between the channel surfaces of the Trombe wall and a modified version of the conventional Trombe wall have been investigated. Velocity profiles, temperature profiles, and pressure defect have been investigated for the conventional Trombe wall, when the temperature of the masonry wall is not uniform but of the form Tw(x) = Tg+Axn. The variation of fluid velocity, temperature and the average Nusselt number have been determined numerically for selected tilt angles of the glass wall for the modified version of the Trombe wall. It was found that there is a significant effect of the glass wall inclination on the average Nusselt number.