~aergy Com~era. Mgmt Vol. 24, No. 3, pp. 237-242, 1984 019@8904/84 $3.00 + 0.00 Printed in Great Britain. All rights reserved Copyright ~ 1984 Pergamon Press Lid YEAR ROUND PERFORMANCE OF THERMOSYPHON SOLAR WATER HEATER IN BENGHAZI M. M. HAWAS and T. MUNEER Industrial/Mechanical Engineering Department Faculty of Engineering, Garyounis University, Benghazi, Libya (Received 9 March 1983) AlUa'act--The relative merits of a thermosyphon heater for domestic water heating are brought to light with special emphasis to Libyan weather conditions. The experimental performance of this type of heater was studied by the authors for a brief period and reported in an earlier study. In the present study, year-round experimental performance is reported. Measurements performed all over the year showed that water is heated to a maximum temperature of 66°C while the minimum temperature during six months was as high as 50°C. The picture is no less bright from an overall efficiency point of view. Efficiency ranges as high as 40 to 50%. Hourly measurements on various days showed that the water temperature has an increasing trend, irrespective of the fluctuating solar radiation pattern on a cloudy day. INTRODUCTION tern throughout the whole year. The main point of interestis the temperature of the heated water obtain- Thermosyphon solar water heaters have been proved able at the end of the day and the overall daily to be well suited for domestic use, especially in rural thermal efficiencyof the system. Another objective is areas. The main drawback of this system is the to study the various system temperatures, solar radi- freezing of water in the collector if subjected to very ation intensity in the collector plane and ambient cold night temperatures, which is not the case in this country or countries with similar climates, temperature on an hourly basis. An experimental and analyticalperformance study ofa thermosyphon heater situated in Benghazi, Libya (a) Day-end temperatureand dailyeJ~iciency has been made by the authors and reported [l].In the For several days in each month, the initialtcm- forementioned study experimental results for a brief perature of the water filled in the system in the period of about 2 months were reported. Solar energy morning and the final water temperature around is a highly variable source of energy, and a long term sunset are measured. No water was drawn off during performance study is necessary. Therefore, it is rcc- the day. Figure I shows the day-end temperature of ommended that a year round performance study of hot-water throughout the year. Data was obtained the system should be made. for 125 days during the year 1982. The maximum This paper is a continuation of the previous one temperature during the entire year was found to be and provides experimental results through l year. 66°C and this occurred on August 31st while the minimum temperature was found to bc 23°C which SYSTEM DESCRIPTION occurred on 7 February. As expected, the water temperature fluctuates considerably in the winter The details of all components of the system (e.g. months, while it is almost steady in the summer collector, storage tank, piping, measuring instru- months. It fluctuates in the winter months from a ments etc.)are reported in Rcf. [l].The main dimen- minimum of 23°C to a maximum of 51°C. In the sions of the system are: summer months this variation is from 50 to 60°C. collector net frontal area: Im' Table I shows the minimum and maximum water single glass cover: 4 mm thick Table I. Monthly minimum and maximum water temperature absorber plate: steel, mat black Water temperature(~C) collector tilt: 30 ° due south Days of storage tank volume: 60 liters Month Initial Monthly max. Monthly rain. measurcmem storage tank insulation: 10cm glass wool Jan 17 51 27 21 Feb 15 49 23 9 all round. May 23 60 48 8 Jun 25 63 55 7 Jul 29 65 58 18 Aug 30 66 58 20 EXPERIMENTAL INVESTIGATION Sep 29 65 60 ]0 Oct 27 59 54 14 The main objective of this experimental study is to Nov 23 48 42 4 obtain the performance of the thermosyphonic sys- Dec 20 49 27 16 237 E.C.M. 24/3----F