A solar still system is designed and built to utilize solar energy in the Gulf States region to produce fresh water from brackish and sea water. This experimental work has been conducted with and without a cooling tub...A solar still system is designed and built to utilize solar energy in the Gulf States region to produce fresh water from brackish and sea water. This experimental work has been conducted with and without a cooling tube. The results showed that the daily production rate of the simple solar still without a cooling tube is slightly higher than that with a cooling tube. This could be due to the fact that the cooling tube has a smaller effective condensation surface area than the glass cover of the simple still. The cooling tube also reduces the solar energy that reaches the water in the still. It might also be due to the fact that the use of a cooling tube has the effect of reducing the average temperature in the solar still cavity. This resulted in reducing the evaporation rate and consequently reduced the production rate.展开更多
This paper presents the simulation models of the plate-fin, air-to-water (or water vapour) heat exchangers used as air-heating or air-cooling and dehumidifying coils in the HVAC (Heating, Ventilation and Air-Condition...This paper presents the simulation models of the plate-fin, air-to-water (or water vapour) heat exchangers used as air-heating or air-cooling and dehumidifying coils in the HVAC (Heating, Ventilation and Air-Conditioning) systems. The thermal models are used to calculate the heat exchange between distributing air and coil pipes and outlet temperatures of air and heat or chilled fluid. The aerodynamic models are used to account for the pressure drop of the air crossing the coil tubes. They can also be used to optimize the structures of such coils. The models are based on principal laws of heat and mass conservation and fluid mechanics. They are transparent and easy to use. In our work, a coil is considered as an assembly of numbers of basic elements in which all the state variables are unique. Therefore we can conveniently simulate the coils with different structures and different geometric parameters. Two modular programs TRNSYS (Transient System Simulation) and ESACAP are utilized as supporting softwares which make the programming and simulation greatly simplified. The coil elements and a real coil were simulated. The results were compared with the data offered by the manufacturer (company SOFICA) and also with those obtained using critical methods such as NTU method, etc. and good agreement is attained.展开更多
文摘A solar still system is designed and built to utilize solar energy in the Gulf States region to produce fresh water from brackish and sea water. This experimental work has been conducted with and without a cooling tube. The results showed that the daily production rate of the simple solar still without a cooling tube is slightly higher than that with a cooling tube. This could be due to the fact that the cooling tube has a smaller effective condensation surface area than the glass cover of the simple still. The cooling tube also reduces the solar energy that reaches the water in the still. It might also be due to the fact that the use of a cooling tube has the effect of reducing the average temperature in the solar still cavity. This resulted in reducing the evaporation rate and consequently reduced the production rate.
文摘This paper presents the simulation models of the plate-fin, air-to-water (or water vapour) heat exchangers used as air-heating or air-cooling and dehumidifying coils in the HVAC (Heating, Ventilation and Air-Conditioning) systems. The thermal models are used to calculate the heat exchange between distributing air and coil pipes and outlet temperatures of air and heat or chilled fluid. The aerodynamic models are used to account for the pressure drop of the air crossing the coil tubes. They can also be used to optimize the structures of such coils. The models are based on principal laws of heat and mass conservation and fluid mechanics. They are transparent and easy to use. In our work, a coil is considered as an assembly of numbers of basic elements in which all the state variables are unique. Therefore we can conveniently simulate the coils with different structures and different geometric parameters. Two modular programs TRNSYS (Transient System Simulation) and ESACAP are utilized as supporting softwares which make the programming and simulation greatly simplified. The coil elements and a real coil were simulated. The results were compared with the data offered by the manufacturer (company SOFICA) and also with those obtained using critical methods such as NTU method, etc. and good agreement is attained.
