Results 1 - 3 of 3
Results 1 - 3 of 3. Search took: 0.014 seconds
|Sort by: date | relevance|
[en] This paper deals with a numerical and experimental investigation of a daily solar storage system conceived and built in Laboratoire de Maitrise des Technologies de l Energie (LMTE, Borj Cedria). This system consists mainly of the storage unit connected to a solar collector unit. The storage unit consists of a wooden case with dimension of 5 m3 (5 m x 1m x 1m) filed with fin sand. Inside the wooden case was buried a network of a polypropylene capillary heat exchanger with an aperture area equal to 5 m2. The heat collection unit consisted of 5 m2 of south-facing solar collector mounted at a 37 degree tilt angle. In order to evaluate the system efficiency during the charging period (during the day) and discharging period (during the night) an energy and exergy analyses were applied. Outdoor experiments were also carried out under varied environmental conditions for several consecutive days. Results showed that during the charging period, the average daily rates of thermal energy and exergy stored in the heat storage unit were 400 and 2.6 W, respectively. It was found that the net energy and exergy efficiencies in the charging period were 32 pour cent and 22 pour cent, respectively. During the discharging period, the average daily rates of the thermal energy and exergy recovered from the heat storage unit were 2 kW and 2.5 kW, respectively. The recovered heat from the heat storage unit was used for the air-heating of a tested room (4 m x 3 m x 3 m). The results showed that 30 pour cent of the total heating requirement of the tested room was obtained from the heat storage system during the whole night in cold seasons
[en] A thermal model has been developed to investigate the potential of using the stored thermal energy of the ground for greenhouse heating and cooling with the help of a ground heat storage system (GHSS) integrated with the greenhouse located in the premises of CRTEn, Tunis, Tunisia. Experiments were conducted extensively throughout the years 2006-2007, and the developed model was validated against several consecutive arbitrary days experiments. The predicted and measured values of the greenhouse air temperatures and humidities that were verified, in terms of root mean square deviation and correlation coefficient, exhibited fair agreement. The results of this study showed that the GHS system kept the inside air temperature 1-3 degree higher than that of outside air at nighttime. The main reason for this low efficiency is due to the weak heat transfer area of the water-air heat exchanger. The simulation results indicate that the GHSS does not yield any significant effect for cooling greenhouses during sunny daytime. The GHSS fulfils its full potential for a heat transfer area of 150 m2. With this area, there occurs 4-6 degree rise of temperature in greenhouse as compared to the temperatures without GHSS and respectively 5-7.5 degree rise in greenhouse as compared to outside air
[en] This paper deals with an experimental study of an inexpensive integrated solar storage collector (ISSC) of total aperture area of 2 m2, used for the providing of domestic hot water. The ISSC is characterised by an absorber matrix made up of a thin cement concrete slab which performs the function of both absorbing and storing of the solar thermal energy. Inside the concrete absorber was embedded a cooper pipe network. Outdoor experiments were carried out under varied environmental conditions for several days during three consecutive months (from November 2007 to February 2008). The experiments were carried out by measuring the climatic variables, temperatures in different parts of the collectors, and mass flow rates of water, during the test days. Based on these measurements, the behavior of the systems was analyzed by comparing exit temperatures, heat losses, and delivered useful energy. A detailed energy and exergy analysis was carried out for evaluating the thermal and optical performance, exergy losses as well as exergetic efficiency for ISSC under given operating conditions. Results shows that the integrated solar storage collector, having energetic and exergetic efficiencies of 32% and 23.5% respectively, provides acceptable stored thermal heat rate by supplying approximately 80% in domestic hot water requirements for a family composed of 5-6 persons. An economic evaluation was made considering the investment time recovery through the system. The results obtained from the ISSC system were compared with the results obtained from a high quality thermosyphon solar system composed of a flat-plate collector (with a total aperture area of 2 m2) and its corresponding insulated storage tank (200 l), tested at the same time.