Performance of a solar collector/storage water heater

This paper presents a general analytical model of a solar collector/storage water heater in which water is flowing at a constant rate between the glass cover and the absorbing plate. The effects of the variations of the depth of water, its flow velocity and the length of the absorbing plate on the performance of the collector have been studied.     

Techno-economic appraisal of an integrated collector/storage solar water heater

Integrated collector/storage solar water heaters, due to their simple compact structure and inherent freeze protection, offer a promising approach for solar water heating in colder climates. Such a system, designed specifically for application at a Northern latitude, has been developed incorporating a heat retaining storage vessel mounted within a concentrating cusp reflector supported by a novel exo-skeleton framework. The performance was determined experimentally under real operational conditions in the Northern Irish climate. A detailed cost analysis is presented and payback periods, substituting different local fuel/power sources, determined.     

Integrated collector storage solar water heater: Temperature stratification

An analysis of the temperature stratification inside an Integrated Collector Storage Solar Water Heater (ICS-SWH) was carried out. The system takes the form of a rectangular-shaped box incorporating the solar collector and storage tank into a single unit and was optimised for simulation in Scottish weather conditions. A 3-month experimental study on the ICS-SWH was undertaken in order to provide empirical data for comparison with the computed results. Using a previously developed macro model; a number of improvements were made. The initial macro model was able to generate corresponding water bulk temperature in the collector with a given hourly incident solar radiation, ambient temperature and inlet water temperature and therefore able to predict ICS-SWH performance. The new model was able to compute the bulk water temperature variation in different SWH collectors for a given aspect ratio and the water temperature along the height of the collector (temperature stratification). Computed longitudinal temperature stratification results obtained were found to be in close agreement with the experimental data.     

Analysis of a black liquid flat plate solar collector

In this paper we present a theoretical model of the black liquid flat plate solar energy collector. Numerical calculations have been performed corresponding to the experiments of Minardi and Chuang (1975). The present model has a good agreement with the experiments of Minardi and Chuang. A study of the effects of varying parameters, such as the liquid flow rate, radius and length of the tube has been made corresponding to the average solar intensity and ambient temperature data of 20 June 1974 in Ohio, U.S.A. The system's performance has also been studied for tropical climates.     

Experimental investigation of a domestic solar water heater with solar collector coupled phase-change energy storage

Phase change materials (PCMs) have good properties such as high thermal capacity and constant phase change temperature. Their potential use in solar energy storage is promising. Tests of exposure and constant flow rate are performed to investigate the thermal performance of a domestic solar water heater with solar collector coupled phase-change energy storage (DSWHSCPHES). Due to the low thermal conductivity and high viscosity of PCM, heat transfer in the PCM module is repressed. The thermal performance of the DSWHSCPHES under exposure is inferior to that of traditional water-in-glass evacuated tube solar water heaters (TWGETSWH) with an identical collector area. DSWHSCPHES also performs more efficiently with a constant flow rate than under the condition of exposure. Radiation and initial water temperature have impacts on system performance; with the increase of proportion of diffuse to global radiation and/or initial water temperature, system performance deteriorates and vice versa.     

Theoretical and experimental studies on collector/storage type solar water heater

Extensive theoretical and experimental studies on a built-in-storage solar water heater which was developed earlier by Garg in India, are carried out. In this water heater the absorber plate performs the dual function of absorbing the solar energy and storing the heated water. In the theoretical study, the transient performance of the system is predicted by solving the mathematical models consisting of energy balance equations which are written on different collector nodes by considering their capacity effects and various heat loss effects. These equations are converted in the finite difference form and then solved by digital computer. Solar radiation and ambient temperature are represented by Fourier series in the theoretical analysis. Its night cooling drawback is somehow checked by covering the collector system by an insulation cover during cooling hours and also by using a insulated baffle plate inside the tank adjacent to the absorber plate. It is observed that by using the insulation cover, the collector performance can be improved by 70 per cent. Use of baffle plate improves the performance during day as well as night time.     

蜂窝热管平板式太阳能热水器的实验研究

把蜂窝技术和热管技术结合起来应用于平板式太阳能热水器，可以大大减少热损失，提高日平均效率。经多次实验证明，蜂窝热管平板式太阳能热水器的日平均效率可以比真空管式热水器的高，热损系数则要小很多，具有推广应用价值。     

Analysis and design of a novel flat plate solar collector

In conventional flat-plate solar collectors, tubes are welded or pressed to a flat-plate. A tubeless flat-plate collector has no tubes welded or pressed to absorber plate. It is merely two-parallel plates made of galvanized steel, and welded to each other. This configuration reduces thermal resistance greatly; a matter which reflects on its efficiency. Those types of collectors proved to be more efficient and economic than conventional flat-plate solar collectors.     

Heat retaining integrated collector storage solar water heater with asymmetric CPC reflector

A novel integrated collector storage solar water heater (ICSSWH) was designed, optically analysed and experimentally studied. The unit was based around a heat retaining ICS vessel design consisting of two concentric cylinders mounted horizontally inside a stationary truncated asymmetric compound parabolic concentrating (CPC) reflector trough. The annulus between the cylinders was partially evacuated and contained a small amount of water, which changed phase at low temperature, producing a vapour and creating a thermal diode transfer mechanism from the outer absorbing surface to the inner storage vessel surface. The absorbing outer vessel surface covered with selective absorber film and was partially exposed to solar radiation. The remaining vessel surface area (including the vessel ends) was thermally insulated to improve heat retention during the night. Curved reflectors with a high reflectance along with high transmittance glazing were also used to improve effective operation of the ICS system. The thermal behaviour of the ICS system was compared to that of a Flat Plate Thermosiphonic Unit (FPTU). The experimental results showed that the ICS system is as effective during daily operation as it is during the night. Furthermore, the thermal loss coefficient during night gives similar values between the ICS system and FPTU.     

Thermal performance of integrated collector storage solar water heater with corrugated absorber surface

An investigation is reported of the thermal performance of an integrated solar water heater with a corrugated absorber surface. The thermal performance of the rectangular collector/storage solar water heater depends significantly on the heat transfer rate between the absorber surface and the water, and on the amount of solar radiation incident on the absorber surface. In this investigation, the surface of the absorber is considered to be corrugated, with small indentation depths, instead of plane. The modified surface has a higher characteristic length for convective heat transfer from the absorber to the water, in addition to having more surface area exposed to solar radiation. The corrugated surface based solar water heater is determined to have a higher operating temperature for longer time than the plane surface. It means during the operation of water heater, more solar energy is converted into useful heat. However, this modification has reduces the efficiency of the system marginally.     

Transient investigation of a two phase closed thermosyphon flat plate solar water heater

This work presents an unsteady state theoretical and experimental investigation of natural circulation two phase closed thermosyphon flat plate solar water heaters. The governing equations of the heater storage tank and connecting pipes are presented and generalized in dimensionless form, while the governing equations of the different components of the collector were previously discussed by the author. Also, the author's earlier simulation program of the collector is modified to include the solution of the dimensionless governing equations of the present analysis. For verifying the modified simulation program, a two phase closed thermosyphon solar water heater is designed, constructed and tested at different meteorological conditions, initial storage tank temperatures and different hot water withdrawal load patterns. The comparison between the experimental results and their corresponding simulated ones shows considerable agreement.     

Optimization of the heat exchanger in a flat plate indirect heating integrated collector storage solar water heating system

Due to the environmental impact of energy usage, consumers need to be encouraged to use renewable energy sources such as solar energy. The indirect heating flat plate integrated collector storage solar water heating system is one of the compact systems for domestic water heating. It incorporates the collection of a solar energy component and a hot water storage component in one unit. The objectives of this study were to investigate the effect of different parameters on the thermal performance of this system with the aim of reducing both the initial and the running costs. The outlet service water temperature was used as a measure of performance, because it is an indicator of the energy acquired from the solar radiation. The continuity, momentum and energy equations of the fluids involved in the system were numerically solved in a steady state condition, using FLUENT software. Three-D CFD models were developed and validated using previous experimental results. A standard k–ω turbulent model was used in the optimization of the heat exchanger because it produced good agreement with the experimental results. The surface-to-surface radiation model was included. The effect of single and double row heat exchangers with different lengths was investigated. Circular and elliptic cross-section pipes were also examined. Mass flow rates of 500 and 650 L/h were chosen. The results showed that the single row HX of 10.8 m length for both the elliptical and type B tube gave high service water outlet temperature (acceptable for heat exchanger design) and with low pumping power. This resulted in an increase in the thermal efficiency and a significant reduction in both the initial and the operating costs of the system.     

Dual functioning flat plate thermal solar collector

The purpose of this paper is to investigate the cost effectiveness of a self-constructed and installed flat plate solar energy collector. The report analyzes the theoretical energy output of the solar collector, the experimental measured energy output and the theoretical insulation properties of the collector as constructed and installed.The results obtained indicate the collector is cost effective because of its insulation property when installed inside a single glazed window. The collector produces a relatively small energy income as a solar energy collector.     

Optimum tilt angle for a flat plate solar collector

One of the important parameters that affects the performance of a flat plate solar collector is its angle of tilt with the horizontal. This is due to the fact that the variation of tilt angle changes the top loss coefficient and the amount of solar radiation reaching the absorber plate. A mathematical model has been developed for calculating the useful energy gained by a flat plate collector under various operating conditions. The model is then used to determine the optimum tilt angles for a typical collector in Basrah on a daily basis, as well as on the basis of a specified period. The optimum tilt angle is found by searching its value for which the useful energy gained by the collector is a maximum for a particular day or a specified period.From the results, it is observed that changing the tilt angle eight times in a year determines the useful energy in Basrah near its value which is found by changing the tilt angle daily to its optimum value. Furthermore, the influence of various operating parameters is studied on the daily optimum tilt angle.     

Single basin solar still coupled with flat plate collector

This paper presents the transient performance of a single basin solar still coupled with a flat plate collector. The average daily production of distilled water has been found to be 24% higher than for a simple single basin solar still     

Performance of an inverted flat plate solar collector

In this note an analysis of an inverted flat plate solar collector has been presented. Effect of various parameters, namely thickness of the insulation, air conductance between flowing water and top of the bottom insulation, length of the collector and flow velocity of water on the performance of the collector have been studied. Numerical calculations have been made for typical cold day in Delhi, namely 26 January 1980.     

Performance analysis and experimental validation of a vee-corrugated absorber integrated collector storage solar water heater

This paper focuses on enhancing the energy collection efficiency of an integrated collector storage solar water heater (ICS SWH) by vee-corrugating the absorber and optimizing the design for the vee-included angle through simulation and experimental study. This paper presents an efficient algorithm for analyzing a vee-corrugated absorber ICS SWH using Engineering Equation Solver Software. For validating this algorithm, two models of ICS SWH systems have been fabricated: one with a flat absorber and the other with a 60° vee-included angle corrugated absorber with eight corrugations. The basic purpose of the fabrication of the flat absorber ICS SWH system was to approximate the absorptivity of the absorber. A typical value of 0.68 was estimated for the absorptivity of the aluminum absorber coated with nonselective black paint. After the experimental investigation of the 60° vee-included angle ICS SWH system, it was found that the real-time readings were in close agreement with the numerical model readings. For comparison with the previous work, a five-corrugation system with an approximate 90° vee-included angle with the same projected dimensions was modeled and the efficiencies of both the models for the time from 7 a.m. to 3 p.m. were calculated. The efficiency of the eight-corrugation model was 42.56%, which was better than the previous work of the five-corrugation model, with a 38.86% efficiency for the same ambient conditions. Also, it was theoretically deduced that we had an optimized system at 18 corrugations and a vee-included angle of 28.78°.     

Optimization of a wickless heat pipe flat plate solar collector

The transient thermal behaviour of wickless heat pipe flat plate solar collectors has been analyzed with regard to various parameters. These parameters include global solar radiation intensity, inlet cooling water temperature, absorber plate material and thickness, ratio of pitch distance to wickless heat pipe diameter and ratio of condenser section length to total wickless heat pipe length. The results show that the selection of an absorber plate having a high value of conduction heat transfer rate per unit temperature difference is limited by the pitch distance.     

Study of a solar water heater using stationary V-trough collector

There are various types of solar water heater system available in the commercial market to fulfill different customers’ demand, such as flat plate collector, concentrating collector, evacuated tube collector and integrated collector storage. A cost effective cum easy fabricated V-trough solar water heater system using forced circulation system is proposed. Integrating the solar absorber with the easily fabricated V-trough reflector can improve the performance of solar water heater system. In this paper, optical analysis, experimental study and cost analysis of the stationary V-trough solar water heater system are presented in details. The experimental result has shown very promising results in both optical efficiency of V-trough reflector and the overall thermal performance of the solar water heater.     

A distributed model for a tedlar-foil flat plate solar collector

A theoretical simulation of flat plate collector performance, with temperature-dependency for material and coolant properties, is presented and the simulation is performed without asserting an a priori value for an overall heat loss coefficient of the collector. This approach differs from many previous works reported in the literature. For a given meteorological condition as well as key design parameters of collector as inputs, the model describes a 2-D absorber plate where its temperature distributions along with the coolant channels can be predicted. A comparison between the theoretical predictions and the experimentally measured data show good agreement to within 4%. The distributed modeling of a collector described in this paper is deemed to be a useful tool for the design of solar collectors.