thermal performance of solar air heaters implementing with PCM still is not ... enhance the performance of flat, finned and v-corrugated solar air heater with.
iii SUMMARY SUMMARY Egypt located in North African Sunbelt region with flat desert topography and perennially has clear skies with high rates of solar intensity throughout the year which favorable to thermal solar energy technologies. The development of sustainable solar energy services for heating purposes like the supply of heating air using solar air collectors may face a great problem at the absence of solar radiation. So, the thermal energy storage is used in overcoming
the periodic and diffused nature of the solar energy. Among the most promising ideas for the storage of solar energy is the exploitation of latent heat of fusion for some organic and inorganic materials known as latent heat storage (LHS) using phase change materials (PCM). It as an effective tool to enhance the thermal performance of solar heating systems. From the previous work, it has been observed that, the investigation of thermal performance of solar air heaters implementing with PCM still is not considered. Besides, using three different geometries of absorber plate named; flat, finned and v-corrugated with the use of PCM as latent heat storage material is still in its developing stage. The aim of this research is to enhance the performance of flat, finned and v-corrugated solar air heater with and without using PCM. Therefore in this thesis, the effect of design and operational parameters are investigated experimentally. The experimental setup is designed and tested under prevailing weather conditions of Tanta city (30o 43/ N, 31oE), Egypt. It consists of centrifugal belower, PVC connection test pipe with gate valve, solar air heater and PCM closed channel beneath the absorber surface of the heater. The air heater with projected area 1 x 1 m2 is conducted on three types of absorbent surfaces. For
iv SUMMARY the flat plate, it is a sheet of copper with thickness 1 mm and area 1×1 m2, while for finned plat, it is also a sheet of copper with thickness 1 mm and area 1m2. There are nine rectangular fins made of copper welded perfectly along its surface longitudinally parallel to the flow direction. The fin height is 2.5 cm; the spacing between two fins is 12.5 cm with a total surface area of 1.33 m2. While for v-corrugated plate, it is also a sheet of copper with thickness 1 mm and total surface area equals 1.8 m2, the height of the v-groove is 2.15 cm and the v-corrugation angle is 60o. The system is suitably instrumented to measure the different climatic and operational parameters like the solar radiation, different temperatures of the solar air heater elements at various positions and the air mass flow rate. The influences of all operating and design parameter on the performance of solar air heater are considered experimentally with and without using PCM. These parameters are: 1-Increasing the heat transfer area of the absorber surface by using finned and v-corrugated absorbent surfaces and compared their performances with flat surface. 2- Studying the effect of change the air mass flow rate on the performance of each heater. 3- Studying the effect of change the thickness of the PCM blew the absorber plate for each heater. 4- The effect of using an insulated upper cover during night hours on the thermal performance of the v-corrugated solar air heater. The other thermal performance parameters which are calculated based on the experimental results are presented also with and without using PCM. These parameters include the temperature difference of air across the heater,
v SUMMARY convective heat transfer coefficient of air, instantaneous thermal efficiency, daily average efficiency and the PCM freezing time. The main results from this thesis are summarized below: 1-When using the PCM, the outlet temperature of the v-corrugated plate solar air heater reaches higher values than ambient temperature by 2-7.2 ºC for 3.5 h after sunset compared with 1.5 –5.5 ºC for 2.5 h and 1–4.5 ºC for 1.5 h for flat and finned plates solar air heater when the air mass flow rate is 0.062 kg/s, respectively. 2- Similarly, the outlet temperature of the v-corrugated plate solar air heater reaches higher values than ambient temperature by 3-13 ºC for 8 h after sunset compared with 2.5–10.5 ºC for 6 h and 2–8.5 ºC for 4 h for flat and finned plate solar air heater when the air mass flow rate is 0.009 kg/s, respectively. 3- When using PCM, the daily efficiency of the v-corrugated solar heater are 62, 52 and 27 % compared with 50, 43.2 and 22.2 % for the same plate heater but, without using PCM at air mass flow rates 0.062, 0.028 and 0.009 kg/s, respectively. 4- When the PCM layer thickness decreases from 4 cm to 2cm , the air temperature difference across the heater is slightly increases during PCM melting process (8:00 am to 4:30 pm) and it slightly decreases during PCM discharging process which extends for hours comparing the case where the thickness of the PCM layer is 4 cm. 5- It is recommended that, the finned solar air collector should be operated at low mass flow rates ≤0.03 kg/s.m2, in which temperature air differences are more observed compared with conventional flat air heater.
vi SUMMARY 6- The performance of solar air heater with built-in PCM as thermal energy storage is improved with insulation of the glass cover surface of the heater from the time of sunset where; the air outlet temperature as well as the PCM freezing time is increased.
ORGANIZATION OF THE THESIS The thesis compromises five chapters and three Appendices as follows:
Chapter 1 include an introduction showing the using of solar air heaters with latent heat storage materials with explaining its principle, classification, properties and applications. Chapter 2 introduces an intensive literature review of the different solar air heater designs without and with using PCM, and the factors that affecting the performance of the solar air heaters. Also it mentions an overview about the types and specifications of the phase change materials. Chapter 3 presents a detailed view of the design and construction of the experimental setup. Also, it is devoted to provide a brief description of the employed measuring instruments, measuring techniques and experimental procedure. Chapter 4 describes the results obtained from experimental work with their discussions. Comparisons between the parameters affecting the thermal performance of the flat, finned and v-corrugated solar air heater are presented with and without PCM. A comparison between current and past works is done which proves a good agreement between them. Chapter 5 includes the conclusions of the present work and the suggestions for future work.
