The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Adnan Shariah - One of the best experts on this subject based on the ideXlab platform.
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Technical note Best connection scheme of collector modules of thermosyphon solar water Heater operated at high temperatures
Renewable Energy, 1999Co-Authors: Adnan Shariah, Deifallah Dajeh, Nabil B. MalhiAbstract:Large scale thermosyphon solar water Heater for high temperature applications is simulated by the use of the Transient Simulation Program (TRNSYS). A daily hot water load of 1500 l/day and 2500 l/day at 80°C was assumed. The hot water is consumed daily from 08·00–17·00 h. A back-up electric Auxiliary Heater was added to the system in two schemes: first, located inside the storage tank with a thermostat; second, outside the tank connected to the heating system between the tank and the facilities. The collector modules were connected in five different schemes: first, all collectors were connected in series in one line, or collectors were connected in two, three, four or five parallel lines each consisting of many collectors. The results showed that the best connection is when the 20 collectors, comprising the system, are connected in two parallel lines each consisting of 10 collectors. It was found that the monthly and yearly useful energy from the system was higher when the Auxiliary water Heater was added to the system outside the storage tank.
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effects of Auxiliary Heater on annual performance of thermosyphon solar water Heater simulated under variable operating conditions
Solar Energy, 1997Co-Authors: Adnan ShariahAbstract:Abstract A thermosyphon solar water heating system with electric Auxiliary Heater was simulated using the TRNSYS simulation program. Location of the Auxiliary Heater, inside the storage tank or connected in series between the system and the user, was studied using the TMY meteorological data for Los Angeles, California. Simulations were performed for two different water load temperatures (60 and 80°C) and for two types of daily hot water volumes (250 and 150 l). Four types of daily hot water consumption profiles were used in the present study, namely; the widely used Rand profile, continuous, evening and morning profiles. Also, the simulation is extended to cover the effects of thermal and optical properties of the flatplate collector and the volume of the storage tank. The results show that if water is drawn on a schedule corresponding to the Rand draw profile, the system operates with higher efficiency when the Auxiliary Heater is located in the storage tank than when the Auxiliary Heater is outside the storage tank. When operated with each of the other three draw schedules, however, better performance is achieved by locating the Auxiliary Heater outside the tank. The increase in solar fraction depends on the load profile and volume, temperature setting, as well as the quality of the collector and the storage tank volume. When the values of the parameters FR(τα)n and FRUL are changed from 0.8 and 16 kJ/h m2°C to 0.6 and 30 kJ/h m2°C, the solar fraction decreases by approximately 40–50%.
D R Wilson - One of the best experts on this subject based on the ideXlab platform.
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simulation studies of the position of the Auxiliary Heater in thermosyphon solar water heating systems
Renewable Energy, 1997Co-Authors: I M Michaelides, D R WilsonAbstract:This paper investigates the effect of the physical location of the Auxiliary source of energy in thermosyphon solar water Heaters and shows that the performance of the system can be optimised with respect to the geometry of the system components. The investigation has been based on a domestic thermosyphon solar water heating system, which was simulated using the TRNSYS programme. The annual solar fraction of the system, at the weather and socioeconomic conditions of Cyprus, is, at best, approximately 77% with an in-tank Auxiliary Heater configuration and 86% with an external Auxiliary Heater. It is demonstrated that the arrangement with the external Auxiliary unit has a higher collector efficiency and results in a higher annual solar fraction. In the case of in-tank Auxiliary, the system performance increases with the height of the Auxiliary position from the bottom of the storage tank; with the Auxiliary at the bottom of the storage tank the annual solar fraction is approximately 59%, compared to 77% when the Auxiliary is located at the top of the tank. The system performance also depends on the height of the collector return from the bottom of the tank.
L S Chan - One of the best experts on this subject based on the ideXlab platform.
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Simulation–optimization of solar-assisted desiccant cooling system for subtropical Hong Kong
Applied Thermal Engineering, 2010Co-Authors: K F Fong, T T Chow, L S ChanAbstract:Abstract Solar cooling is a novel approach, which primarily makes use of solar energy, instead of electricity, to drive the air-conditioning systems. In this study, solar-assisted desiccant cooling system (SADCS) was designed to handle the cooling load of typical office in the subtropical Hong Kong, in which half of the building energy is consumed by the air-conditioning systems. The SADCS mainly consisted of desiccant wheel, thermal wheel, evaporative coolers, solar air collectors and gas-fired Auxiliary Heater, it could directly tackle both the space load and ventilation load. Since the supply air flow is same as the outdoor air flow, the SADCS has a feature of sufficient ventilation that enhances the indoor air quality. Although it is inevitable to involve the Auxiliary Heater for regeneration of desiccant wheel, it is possible to minimize its usage by the optimal design and control scheme of the SADCS. Through simulation–optimization approach, the SADCS can provide a satisfactory performance in the subtropical Hong Kong.
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Simulation-optimization of solar-assisted desiccant cooling system for subtropical Hong Kong
Applied Thermal Engineering, 2010Co-Authors: K F Fong, Z. Lin, T T Chow, L S ChanAbstract:Solar cooling is a novel approach, which primarily makes use of solar energy, instead of electricity, to drive the air-conditioning systems. In this study, solar-assisted desiccant cooling system (SADCS) was designed to handle the cooling load of typical office in the subtropical Hong Kong, in which half of the building energy is consumed by the air-conditioning systems. The SADCS mainly consisted of desiccant wheel, thermal wheel, evaporative coolers, solar air collectors and gas-fired Auxiliary Heater, it could directly tackle both the space load and ventilation load. Since the supply air flow is same as the outdoor air flow, the SADCS has a feature of sufficient ventilation that enhances the indoor air quality. Although it is inevitable to involve the Auxiliary Heater for regeneration of desiccant wheel, it is possible to minimize its usage by the optimal design and control scheme of the SADCS. Through simulation-optimization approach, the SADCS can provide a satisfactory performance in the subtropical Hong Kong. ?? 2009 Elsevier Ltd. All rights reserved.
R. S. Misra - One of the best experts on this subject based on the ideXlab platform.
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Techno-economic optimization of thermosyphonic solar hybrid water heating systems
Energy Conversion and Management, 1994Co-Authors: R. S. MisraAbstract:All water heating solar systems can be designed on criteria such as technical performance corresponding to the minimum radiation level and the minimum temperature of the ambient air. The quantity of ultimate importance is the cost of energy delivered, which has to be optimized along with collector area and storage tank capacity by optimal mixing of conventional energy (by electrical Heater or boiler) and non-conventional energy by using solar energy collection devices (hybrid energy analysis). Considering this aspect, a simple techno-economic analysis has been developed with the help of a thermal transient model for finding the technical performance of solar energy systems for calculating the percentage of solar energy contribution for a given consumer hot water demand, at a desired temperature for domestic purposes, using a heat exchanger in the collector loop or without a heat exchanger, and for climatic conditions, as in India. A numerical computation has been done for Indian market conditions and climates, as in Delhi. It has been found that the cost of hybrid energy systems is less than for conventional heating systems. The use of an Auxiliary Heater inside the storage tank results in wastage of energy due to the larger heat loss from the storage tank because the storage tank is always kept at the desired temperature, and hence, the Auxiliary energy consumption is higher. It is observed that the use of an Auxiliary Heater at the load point is economically feasible. In some areas, where the water quality is bad, it is essential to use a heat exchanger in the collector loop with demineralized water. For very cold climates, the use of an antifreeze solution in the collector loop with a heat exchanger and a separate storage tank is recommended. For forced flow water heating systems used for industrial process heat, the cost of useful energy delivered is 15% higher. © 1994.
Fu Zhao - One of the best experts on this subject based on the ideXlab platform.
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economic and environmental life cycle analysis of solar hot water systems in the united states
Energy and Buildings, 2012Co-Authors: Yin Hang, Ming Qu, Fu ZhaoAbstract:Abstract This paper evaluates the solar water heating systems for the U.S. typical residential buildings, from the energetic, economic and environmental perspectives, and includes two different types of solar collectors (i.e. flat-plate and evacuated-tube solar collectors), two types of Auxiliary systems (i.e. natural gas and electricity), and three different locations (i.e. Los Angeles, Atlanta, and Chicago). The performance of solar water heating systems is also compared with conventional systems that use either natural gas or electricity. The results showed that the flat-plate solar water heating systems using natural gas Auxiliary Heater has the best performance among all the types and at all locations. The energetic and environmental payback periods for solar water heating systems are less than half of a year, and the life cycle cost payback for solar water heating systems vary from 4 to 13 years for different cities and different configurations when using the conventional electrical water heating system in each city as the benchmark. For a representative case, i.e. flat-plate solar water heating system with natural gas Auxiliary Heater in Atlanta, sensitivity analysis shows that the daily hot water use has the most significant effects on energetic, environmental and economic performance.
