A. Venkatesh

Heat-transfer analysis of a flat-plate collector in a solar thermal pump

A solar thermal water pump using a flat-plate collector with n-pentane as the working fluid is described. A heat-transfer analysis has been carried out for this system with account for all heat losses. Variations in temperature and pressure of pentane in the collection system with time are predicted. Two different situations are considered: one with pentane getting heated without its vapour being used for operation of the pump and the other with pentane vapour used for pump operation during the heating period. Variations in collector efficiency with time are discussed.

Thermodynamic analysis of a solar thermal water pump

Abstract The principle of the workings of a solar thermal water pump with n-pentane as the working fluid is described briefly. The performance of the pump is predicted from the thermodynamic analysis of the cycle of events. Experiments were carried out with a small solar thermal pump having a collector area of 1 m 2 . The experimental and theoretical results were compared. The experimental results were different from those obtained theoretically for ideal conditions. But, during the course of experimentation a number of constraints were noticed. When the theoretical analysis was appropriately modified to account for these limitations, the resulting agreement was found to be good which validates the model proposed.

A solar thermal water pump

The pump employs pentane as the working substance -- an organic fluid with a low boiling point. A flat-plate solar collector generates vapour and its pressure is adequate to pump water from a well. Provision of a separate tank for storing the vapour under pressure improves the performance of the pump. Experiments prove its feasibility and yield useful performance characteristics.

The importance of the condenser in a solar water pump

A brief description of the operation and analysis of a solar water pump is given. It is shown that one of the parameters affecting the performance of the pump is the time taken for condensation of the working fluid in each cycle. The condensation time in each cycle is determined through heat transfer analysis of the condenser. The effects of inlet water temperature and mass flow rate of the cooling water to the condenser on the condensation time and the pump performance have been studied and discussed.

A two stage intermittent solar refrigeration system—Evaluation of salient parameters

Abstract A two stage intermittent solar refrigeration system is described briefly. In such a system, when flat-plate collectors are used for generation, it is very likely that the two generation temperatures are around the same value. The successful operation of the cycle under such conditions depends upon the proper selection of the initial solution concentrations in the high and low pressure generators and the volume ratio of the generators. These parameters have been evaluated with the help of the thermodynamic analysis of the refrigeration cycle operating with ammonia as the refrigerant and water as the absorbent.

Optical analysis of a cylindrical absorber in a fixed spherical reflector

A spherical reflector-distributed-focus system can be effectively used for the collection of solar energy. The absorber, which is always pointing towards the sun and whose axis passes through the centre of curvature of the reflector, tracks the sun continuously for maximum collection of solar radiation.

Experimental observations on a continuous flow type domestic solar water heater

Abstract The operation of a continuous flow type domestic solar water heater is explained with the help of a schematic diagram. Steady state thermal analysis of such a water heater is carried out. A water heater of this type with a collector area of 1 m2 is subjected to tests. The experimental results are compared with predicted results. The experimental results have also been compared with those obtained from a water heater operating on thermosiphon flow. The performance of the continuous flow type water heater is shown to be comparable to that of the thermosiphon flow type. It is concluded that, in the Indian context, the continuous flow type water heater has more advantages than the thermosiphon flow type water heater in view of its low capital cost and the ease of operation and maintenance.

Analysis of a fixed spherical reflector exposed to oblique incident rays

Abstract A fixed spherical reflector tracking absorber solar collector, popularly known as Fixed Mirror Distributed Focus (FMDF) collector, is described. An analysis has been performed to study the variations in optical concentration along the absorber. Optical concentrations have been determined for cases when the sun rays strike the reflector obliquely and have been compared with the values obtained for a noon condition when the sun rays would be normal to the reflector. An elemental ring on the reflector surface is taken up for analysis to determine the useful area of the reflector that would reflect the incident rays towards the absorber. The area of the sector of the elemental ring which illuminates the absorber is determined. The effect of the reflectivity on the optical concentration is also studied. The predicted values are indirectly compared with experimentally measured surface temperatures along the absorber of a laboratory FMDF unit.

Experimental studies on heat transfer in the flat-plate collector of a solar pump

Measured values of temperature and pressure of pentane in the collection system of a laboratory model solar thermal water pump are reported. In one set of experiments the pentane was merely heated without tapping the vapour for pump operation and in the other actual pump operation was performed. Theoretical values evaluated using the model already proposed by the authors, are found to agree well with experimental results.

Domestic solar water heater—continuous flow type

Abstract Problems in domestic solar water heaters, operating on thermosiphon flow, are discussed. A continuous flow type water heater is suggested which will overcome the problems in the thermosiphon flow water heater. Thermal analysis of such a system is carried out for winter and summer performances. The performance of the continuous flow type water heater is comparable to that of the thermosiphon flow type. It is concluded that, in the Indian context, the continuous flow type water heater has more advantages than the thermosiphon flow type water heater. The initial cost of the former is less than that of the latter type. Also, the operation and maintenance of the continuous flow type is simple.