The effect of a baffle plate on the transient performance of a shallow solar pond water heater

A straightforward transient analysis of a shallow solar pond (SSP) water heater fitted with a baffle plate has been presented. In order to study the performance of the system, numerical calculations have been made for a typical cold day in Delhi, viz. 18 Dec. 1984. It is concluded that the SSP can also be used as a built-in storage water heater, with better performance being achieved with the use of a baffle plate.     

Thermal performance study of integrated cold plate with power module

A novel cold plate for cooling of the electronic components with high heat flux and high heat dissipation requirements is proposed. The cold-plate structure of the S-type with guide plates is introduced to avoid the heat hot concentration and increase the heat transfer area. The experimental results show that the maximum chip temperature of the novel cold plate is approximately 40% lower than those of the conventional cold plate. Thermal performance optimizations are conducted, indicating that it is extremely effective to install the heat source on two sides of the cold plate. Compared with the single-side heat source, the maximum chip temperature is increased only 20%. However, the heat dissipation is doubled in the limited space for the double-sides arrangement heat source. Moreover, the integrated density of the power module is greatly enhanced by using the cold plate. Transient state temperature variation indicates that the cold plate have quick thermal response in start-up process. It is beneficial to the heat dissipation of integrated module for high power density.     

Non-isothermal transport phenomenon and cell performance of a cathodic PEM fuel cell with a baffle plate in a tapered channel

This study uses a projection finite element analysis with an element-by-element preconditioned conjugate gradient method to investigate the non-isothermal tapered flow channel installed with a baffle plate for enhancing cell performance in the cathodic side of a PEMFC. The parameters studies including tapered ratio (0.25 ∼ 1.0) and gap ratio (0.005 ∼ 0.2) on the cell performance have been explored in detail. The results indicate that the stronger composite effect of tapered flow channel and baffle blockage provides a better convection heat transfer performance and a higher fuel flow velocity and thus enhances the cell performance.     

Effect of the baffle plate on transient performance of built-in-storage water heater

This communication presents a study on the effects of variation in the inlet and outlet vent area of the baffle plate, variation in the thickness of upper and lower water columns and use of an insulation cover during the night on the transient variation of water temperature of a built-in-storage solar water heater. The effect of duration of water flow rate in the lower column on its performance has also been studied. Numerical calculations have been made for a typical day in Delhi for December 1979.     

Flow structure and flame stability in a micro can combustor with a baffle plate

Flow structure and flame stability to be formed inside a micro can combustor, with a baffle plate having a central fuel nozzle and multi air holes located annularly were investigated experimentally. The structures of the isothermal flow and the reacting flow behind the baffle plate are measured by using a particle image velocimetry (PIV). The result shows that generation of the flow recirculation region enhances the mixing most effectively and is useful to make the combustion chamber compact. However, for the reacting flow condition, the flow structure behind the baffle plate will be changed drastically. The flame stabilization mechanisms have to be discussed in terms of local conditions of fuel and air mixing, flame propagation speed, and so on. These local structures seem to play an important role for the lifted flame location and stability of this type of burner.     

Performance of a portable mini solar-pond

For the present experiments, such a pond was located at JUST, i.e. at 32°N latitude. Its walls were inclined at 45° to the horizontal. The pond was built of galvanized steel (1.44 mm thick) with a circular surface area and total depth of 1 m² and 500 mm, respectively. The effects of the solar-pond's depth and its water's salinity on the store's temperature distributions were determined experimentally and compared with theoretical predictions. A dimensional analysis was carried out to show the effect of the mini solar-pond's size on its thermal behaviour.     

Thermal performance of gas-filled flat plate solar collectors

A sealed space between absorber and cover glass in a flat plate solar collector makes it possible to reduce the influence of humidity condensate and dust at the same time as the enclosed space can be filled with a suitable gas for lowering the heat losses. This article describes the influence of different gases on the heat losses in a typical flat plate solar collector. A model of a gas-filled flat plate solar collector was built in Matlab with standard heat transfer formulas. The results show that the overall heat loss can be reduced by up to 20% when changing from air to an inert gas. It is further possible to reduce the distance between absorber and cover in order to reduce the mechanical stresses in the material with similar heat losses.     

The effect of triangular shutter type flow deflector perforated baffle plate on the thermofluid performance of a heat exchanger

The study aimed to investigate the heat transfer (HT) properties of a tubular heat exchanger (HX) by using innovative baffle plate arrangements. The newly designed baffle plate was circular with triangular openings and adjustable triangular flow deflectors. These deflectors were strategically placed at the inlet of the HX to create a swirling flow downstream. Three baffle plates were installed along the flow direction with different length-to-diameter ratios (pitch ratios) to assess their impact on HT, pressure drop, and thermal enhancement factor. The study compared these results with a smooth channel under varying Reynolds numbers (16,500–29,500). The findings revealed that both the pitch ratio (0.6–1.2) and the inclination angle of the deflectors (30⁰–50⁰) significantly affected the HX's performance. Notably, the baffle plate with a deflector inclination angle of 30° and a pitch ratio of 1 showed a remarkable average improvement of 36.5% compared to other angles and ratios.     

Thermal performance of a solar cooker integrated vacuum-tube collector with heat pipes containing different refrigerants

A solar cooking system using vacuum-tube collectors with heat pipes containing a refrigerant as working fluid has been fabricated, and its performance has been analysed experimentally. The experiments were conducted during clear days in July and August of 2002 in Elazı , Turkey under similar meteorological conditions for three refrigerants and water. Detailed temperature distributions and their time dependences were measured. The maximum temperature obtained in a pot containing 7 l of edible oil was 175 °C. Also, the cooker was successfully used to cook several foods. The cooking processes were performed with the cooker in 27–70 min periods.     

Thermal performance modeling of the reverse absorber shallow solar pond

Reverse absorber type shallow solar ponds are proposed as being capable of attaining higher temperatures and still higher efficiencies than the conventional type due to convection suppression and elimination of top radiative losses. The theoretical thermal analysis and simulation of the performance of two configurations of the reverse absorber shallow solar pond (RASSP); one with the top insulated and the other with top exposed, are presented. The ensuing model equations were solved to obtain the desired performance parameters. For a pond depth of 0.10 m, results of the simulations show that water temperatures up to 70°C could be obtained in a RASSP with double glass covers, higher than could be gotten in either an RASSP with top insulation or a conventional SSP of equal depth. The effect of pond depth on the proportions of the radiation incident on the RASSP that is either collected as thermal energy or lost was studied. The average transmissivity-absorptivity products, (τα), overall heat loss coefficients, UL and optimal pond depths were also computed.     

Numerical simulation on the performance of trisection helical baffle heat exchangers with small baffle incline angles

ABSTRACT

Numerical simulation was conducted on oil–water heat transfer in five circumferential overlap trisection helical baffle shell–and–tube heat exchangers (cothSTHXs) with 16 tubes and incline angles of 12°, 16°, 20°, 24°, and 28° and a segmental baffle heat exchanger of the identical tube layout for comparison under laminar flow calculation conditions. The local images represent shell-side flow patterns, and heat transfer properties are presented showing the detailed “secondary vortex flow” and “shortcut leakage flow” patterns to explain the different characteristics of the six schemes. The simulation curves of the heat transfer coefficient and pressure drop are compared with those of the experimental ones, with satisfactory agreement. The average values of the shell-side heat transfer coefficient and the comprehensive index h_o/Δp_o of the 12° helical scheme are respectively 47% and 51% higher than those of the segmental baffle scheme with about the same pressure drop.     

Thermal performance enhancement of solar air heaters,by a fan-blown absorber plate with rectangular fins

The aim of this study is to provide a remedy for the low thermophysical properties of air, which is used as a fluid of transfer in solar collectors. A fully developed flow needs to be created by the use of staggered fin rows soldered under the absorber plate. The fluid flow undergoes contractions followed by expansions, which creates a fully developed turbulent flow, and increases the thermal heat transfer between the absorber plate and the air. The fins increase the heat transfer surface, from which an appreciable improvement of the thermal heat performance of solar air heaters has been found in comparison to those of solar air heaters with a plane absorber. In this work we have tested the influence of the dimension of the fins and the influence of the space between consecutive fin rows mounted in staggered rows.     

Thermal performance optimization of a flat plate solar air heater using genetic algorithm

Thermal performance of solar air heater is low and different techniques are adopted to increase the performance of solar air heaters, such as: fins, artificial roughness etc. In this paper an attempt has been done to optimize the thermal performance of flat plate solar air heater by considering the different system and operating parameters to obtain maximum thermal performance. Thermal performance is obtained for different Reynolds number, emissivity of the plate, tilt angle and number of glass plates by using genetic algorithm.     

Thermal analysis on the cooling performance of a porous evaporative plate for building

In this paper, a wet porous cooling plate has been used for a building wall. Cooling can be achieved due to the evaporation in the porous layer. A mathematical model on the heat and mass transfer in the unsaturated porous media is developed to analyze the influences of ambient conditions and the porous layer thickness on the cooling performance of the porous evaporative plate. With a decrease in ambient relative humidity and an increase in ambient temperature, more cooling of the porous evaporative plate can be supplied for the inside of the room. The heat exchange between the inside surface of the porous plate and the air in the room should be intensified to achieve a higher cooling efficiency of the porous plate. The ambient wind speed and the thickness of the porous plate also have significant influence on the average temperature of the porous plate. All these results should be taken into account for the utilization of the porous evaporative cooling plate. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20284     

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.     

Thermal performance investigation of double pass-finned plate solar air heater

In this paper, the double pass-finned plate solar air heater was investigated theoretically and experimentally. An analytical model for the air heater was presented. Numerical calculations had been performed under Tanta (latitude, 30° 47′N and longitude, 31°E) prevailing weather conditions. The theoretical predictions indicated that the agreement with the measured performance is fairly good. Comparisons between the measured outlet temperatures of flowing air, temperature of the absorber plate and output power of the double pass-finned and v-corrugated plate solar air heaters were also presented. The effect of mass flow rates of air on pressure drop, thermal and thermohydraulic efficiencies of the double pass-finned and v-corrugated plate solar air heaters were also investigated. The results showed that the double pass v-corrugated plate solar air heater is 9.3–11.9% more efficient compared to the double pass-finned plate solar air heater. It was also indicated that the peak values of the thermohydraulic efficiencies of the double pass-finned and v-corrugated plate solar air heaters were obtained when the mass flow rates of the flowing air equal 0.0125 and 0.0225 kg/s, respectively.     

Experimental and numerical analysis of sodium-carbonate salt gradient solar-pond performance under simulated solar-radiation

The objective of this study is to investigate experimentally and theoretically whether sodium carbonate (Na₂CO₃) salt is suitable for establishing a salinity gradient in a salt-gradient solar-pond (SGSP). For this purpose, a small-scale prismatic solar-pond was constructed. Experiments were conducted in the laboratory under the incident radiation from two halogen-lamps acting as a solar simulator. Furthermore, a one-dimensional transient mathematical model that describes the heat and mass transfer behaviour of the SGSP was developed. The differential equations obtained were solved numerically using a finite-difference method. It was found from the experiments that the density gradient, achieved using sodium carbonate salt, can suppress convection from the bottom to the surface of the pond.     

Thermal performance of PCM thermal storage unit for a roof integrated solar heating system

The thermal performance of a phase change thermal storage unit is analysed and discussed. The storage unit is a component of a roof integrated solar heating system being developed for space heating of a home. The unit consists of several layers of phase change material (PCM) slabs with a melting temperature of 29 °C. Warm air delivered by a roof integrated collector is passed through the spaces between the PCM layers to charge the storage unit. The stored heat is utilised to heat ambient air before being admitted to a living space. The study is based on both experimental results and a theoretical two dimensional mathematical model of the PCM employed to analyse the transient thermal behaviour of the storage unit during the charge and discharge periods. The analysis takes into account the effects of sensible heat which exists when the initial temperature of the PCM is well below or above the melting point during melting or freezing. The significance of natural convection occurring inside the PCM on the heat transfer rate during melting which was previously suspected as the cause of faster melting process in one of the experiments is discussed. The results are compared with a previous analysis based on a one dimensional model which neglected the effect of sensible heat. A comparison with experimental results for a specific geometry is also made.