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[en] A new experimental method for the measurement of bond conductance between the absorber plate the tube of a solar collector was developed. It consists of generating a measured heat flux via an electric resistance heater to simulate solar energy input to the absorber plate. This heat is absorbed by a fluid flowing through the tube and that is also measured. By comparing the energy generated and the energy absorbed, the bond conductance was estimated. Experimental and theoretical methods were compared for absorber plates which contain grooves and tubes embedded to them. Five samples of locally-made fin-and-tube configurations were tested and their bond conductance was found. It was found that the bond conductance of those samples ranged from 6.3 to 1.8 W/m K and that the high conductance was made possible by using the press-fit method in manufacturing those collectors
[en] A portable solar water heater was designed, built and tested. This application of solar energy devices is particularly important for the Bedouin community which can gain a great deal from the solar energy that is continuously available in the desert. It can be also used by campers and those who use recreation vehicles. A normal satellite dish of 150 cm diameter was used as a concentrator for solar radiation. The surface of the dish was covered with reflective aluminum foil which was used to concentrate solar energy on a cooking pot in one mode of operation. This mode was operated in two ways: one with bare pot and the other with the pot being covered with glazing by putting it inside a glass box. The device was also used in another mode of operation to heat water for domestic use by placing a specially designed solar collector in the focus. It was found that, when the device was operated in the bare cooker mode, a 7 kg of water at 20 deg. C was brought to a boil in 1 h. Putting the pot inside the glass box reduced the time required for boiling to 40 min and the cooking power was increased by 275%. In the collector mode, the device was able to heat 30 kg of water from 20 deg. C to 50 deg. C in 21/2 h. The highest efficiency obtained for this mode was 77% and the slope of the efficiency curve was -10.63 W/m2 deg. C.
[en] Highlights: ► Which is better, to operate a heating system continuously under low boiler temperature or intermittently otherwise. ► Previous investigations were based on different building and operating conditions, such as those of Europe. ► Optimum boiler operation for different levels of insulations was obtained for Jordan. - Abstract: In this work, a comparative study of continuous versus intermittent heating in homes was performed. The thermal response factor and intermittent heating factor was found for a typical apartment building in Amman, Jordan. A comparison between several wall, roof, and floor constructions and several levels of insulation thickness was made and the heating load calculations for those constructions (steady state analysis and dynamic behavior) were performed. It was found that more comfort and more fuel saving and less initial and running costs were achieved when continuous heating at low temperature was adopted. Also, the optimization of continuous and intermittent heating was studied in order to minimize fuel economy and maximize thermal comfort. It was found that for high insulated apartment buildings, the continuous operation of the boiler at low water temperature is more economical than when it is operated intermittently at high temperature for more than 14 h per day.