Investigation Of Thermal Performance Research Articles

An Efficient Unified Approach for Performance Analysis of Functionally Graded Annular Fin with Multiple Variable Parameters

The present work investigates the performance of an annular fin of constant thickness, made up of a functionally graded material (FGM). The fin surfaces are exposed in an environment where the heat loss occurs through convection and radiation. The various parameters, describing the fin performances, are considered to be varying with the local temperature and fin radius. An efficient and unified approach, homotopy perturbation method (HPM), is applied for obtaining the closed form solution from the non-linear heat transfer equation of equilibrium. The effects of key thermal parameters, i.e. thermo-geometric, conduction— radiation, thermal conductivity variation, heat generation, exponent of heat transfer co-efficient and the parameter of surface emissivity are explored on the temperature field leading to an overall investigation of thermal performance. And, the effects of such parameters on heat transfer rate, efficiency, effectiveness and temperature distributions are found to be significant. The accuracy of the present closed form solution is measured when its results are verified with the results of FEM and FDM solutions. The present results agree very well with those of FDM results and FEM results which is obtained using COMSOL software.

Experimental and numerical investigation of taper helical and spiral tube thermal performance

This paper presents the comparative experimental and numerical study of heat exchange through tapers helical and spiral tube. The efficiency of heat exchange is increase the thermal performance as well as productivity. The main study was a focus on these two shapes of pipe at various process parameters like mass flow rate and inlet temperature conditions. Co-relation equations were developed for both shapes of pipe with a linear fitting tool available in MATLAB coding software. Proper instrumentation and calibration were taken care in this work. The simple horizontal pipe was used to validate the experimental results with computational fluid dynamics (CFD) results. Experimental validation proves that CFD is an effective tool for thermal performance investigation. The main conclusion of present work was that spiral tube displays enhanced thermal enhancement than the helical tube for all process conditions. Thermal contours are also developed for more detailed study on both shapes of the tube.

Investigation of thermal and electrical performances of a combined semi-transparent PV-vacuum glazing

Combined semi-transparent PV-vacuum glazing provides low overall heat transfer coefficient, reduces solar heat gain, generates clean electricity and admits comfortable daylight. In this work, thermal and electrical performances of a multicrystalline silicon based PV-vacuum glazing were characterised using indoor test cell. For this particular combined system, PV covered 32% of the glazing area. Two different combinations of PV-vacuum glazing systems were manufactured where for the first case vacuum glazing faced test cell external environment (VPS) and for the second case vacuum glazing faced test cell internal environment (SPV). SPV type was found to have superior performance as PV cell achieved lower temperature than VPS type after 125 min exposure under 1000 W/m2 constant intensity from a simulator. For this type PV-vacuum glazing, overall heat transfer coefficient (U-value) was 0.8 W/m2 K and the solar factor was 0.42. U-value of this PV-vacuum glazing was 66% lower and the solar factor was 46% lower than PV double-glazing. Close power drop from PV due to elevated temperature was observed for both PV-double and PV-vacuum glazing.

A Numerical Investigation of Thermal Performance of Earth–Air Heat Exchanger

Today, earth–air heat exchangers (EAHEs) are important heat exchangers used in the air-conditioning of buildings and can be seen in different types and capacities. Thermal comfort is perceived as the comfort of human beings under given room conditions, namely average temperature and relative humidity. For example, the value of average comfort temperature in a room is between 294 and 296 K. The main objective of this analysis is not to obtain the lower air temperature of medium, rather to obtain comfort temperature interval of 294–296 K. This thermal comfort temperature has been achieved at nearly all channel outlets in 1 m depth. For the numerical analysis of EAHE, the maximum mean air temperature of July of the city of Elazig was used. Computational fluid dynamics ANSYS FLUENT 12.1 program was chosen to examine the thermal comfort condition of a typical building. In the analysis of the thermal performance of the EAHE, examinations were made for different earth depths ( $$H = 1$$ , 2, 3 m). PVC was chosen as the EAHE channel material. The numerical model was solved in three dimensions in the steady-state condition using different Reynolds number values ( $$Re = 5\times 10^{3}, 10^{4}, 15\times 10^{3}, 2\times 10^{4}, 4\times 10^{4}, 6\times 10^{4}, 10^{5}$$ ) in the turbulent flow. It was determined that the best thermal performance is at the smallest air inlet velocity. According to the numerical results, it was found that the cooling energy consumption required to provide thermal comfort condition for the typical building is reduced.

Numerical investigation of pin-fin thermal performance for staggered and inline arrays at low Reynolds number

Numerical investigation of pin-fin thermal performance for staggered and inline arrays at low Reynolds number

A novel truncated cone helix energy pile: Numerical and laboratory investigations of thermal performance

As for the cylinder helix energy pile (CyHEP), in order to reduce thermal interference and improve heat transfer efficiency, a novel truncated cone helix energy pile (CoHEP) was proposed in this paper. A 3-D numerical model both considering the dynamic surface condition and the initial soil temperature distribution was developed to investigate its thermal performance, and three main influencing factors (inlet water temperature, water flow rate, cone angle) were studied by the established model. In addition, the laboratory investigation was carried out to verify the accuracy of the numerical model. The results indicate that the heat flux per unit pipe length of the 20° cone angle CoHEP is 6.16% larger than the traditional CyHEP. The whole pipe of CoHEP can be divided into four stages along the flow direction of the pipe length: the entrance stage → the thermal short circuit stage → the small temperature difference stage → the exit stage. During the design of CoHEP, the proportion of the thermal short circuit stage and the small temperature difference stage should be reduced to ensure the overall heat transfer capability. Heat flux per unit pipe length of the CoHEP increases linearly with the inlet water temperature. Increasing the water flow rate can increase the heat flux per unit pipe length of the CoHEP, but it can also reduce the flow time in the pipe, resulting in insufficient heat exchange. As for the cone angle, increasing the cone angle can effectively reduce the radial thermal interference at the upper part of CoHEP and the axial thermal interference. When the system running time is 12 h, as the cone angle increases from 0° to 10° to 20°, the growth rates of heat flux per unit pipe length are 2.54% and 3.53% respectively. Moreover, there must be an allowable maximum cone angle considering the minimum spiral radius of PE pipe, for example, the allowable optimal cone angle is 21° for the model built in the paper.

Performance analysis of an array of square micro-fins

Array of micro pin fin heat sinks shows higher thermal efficiency in high heat flux and critical devices such as aerospace, microelectronic etc. In this work, an array of micro square pin fins has been designed and for this copper is selected as workpiece material. Moreover, a numerical investigation of thermal performances and mechanical behavior of the designed fins has been carried out. The effects of Reynolds numbers on velocity profile and heat transfer performance have also been studied. Additionally, the equivalent (von-Mises) stress along with the structural and total deformations have been observed at the desired pressure applied on the surface of the pin fins. Numerical simulations with similar parametric conditions have also been conducted on a plate having the same dimensions without fins, and a comparison has been made with a plate having micro-fins. It has been observed that the array of square micro pin fins gives a better thermal performance than that of without fins.

Investigation of Thermal Performance of Heat Pipe Heat Exchanger for Waste Heat Recovery

Investigation of Thermal Performance of Heat Pipe Heat Exchanger for Waste Heat Recovery

Numerical investigation of thermal and optical performance of window units filled with nanoparticle enhanced PCM

Filling window units with phase change material (PCM) improves the thermal performance of windows, but on the other hand it has a deteriorative effect on the optical performance due to poor heat conductivity of PCM. A novel method to tackle this drawback of PCM is to disperse nanoparticles in the PCM. In this study, a model was developed to evaluate the thermal and optical performances of window units filled with nanoparticle enhanced PCM (NePCM). The effect of different types of nanoparticles, volume fractions of nanoparticles and sizes of nanoparticles on the thermal and optical performances of windows such as temperature, heat flux, solar transmittance, absorptance and reflectance were numerically investigated and compared with the referent case (i.e. pure PCM). The results showed that the optical and thermal performances of window units filled with nanoparticle dispersed paraffin wax are improved compared to that of with pure paraffin. However, the improvement is nearly the same regardless of nanoparticle type. The effect of volume fraction and size of nanoparticle is significant during the sunset and sunrise periods. Considering both thermal and optical performances of window units, it is recommended to disperse CuO nanoparticles with the volume fraction of below 1% and nanoparticle size of below 15 nm in PCM.

Thermal performance investigation of a PCM-enhanced wall/roof in northern Morocco

Energy efficiency improvement in building sector has become a real challenge in Morocco, especially in the northern region evolving a rapid urban growth. In this context, using the phase change materials (PCM) in the construction is presented as one of the promising solutions to enhance the thermal behaviour of building envelope. This work aims to investigate the thermal performance of a PCM integrated external wall and roof under the summer climate conditions of northern Morocco. Dynamic thermal characterization methodology is adopted through the calculation of decrement factor (DF) and time lag (TL) parameters. For that, a one-dimensional numerical model based on resistance–capacitance (RC) approach is developed and implicitly solved to simulate the heat transfer process through a wall/roof structure. The model is validated through a new small-scale experimental device. Different qualities of PCM, regarding its peak phase change temperature, have been evaluated. Moreover, the PCM layer emplacement within the wall/roof structure was evaluated considering two possible configurations. The obtained results show a significative enhancement of the thermal performance of different wall facades and roof through the use of the suitable PCM quality. An appropriate selection of PCM layer emplacement yields an evidenced enhancement in the case of the roof. As for the walls, the integration of PCM from the interior side increase the TL period but has a negative impact on the DF parameter.

Investigation of thermal performance of unidirectional flow porous bed solar air heater using MLP, GRNN, and RBF models of ANN technique

In the present work, Multi-layer perceptron (MLP), Generalized regression neural network (GRNN), Radial basis function (RBF) and Multiple linear regression (MLR) models has been used to predict the thermal performance of unidirectional flow porous bed solar air heater. These four models have been constructed on the basis of actual experimental data and calculated values. Total 96 experimental data sets have been used in the present work. In GRNN, RBF and MLP models, six input parameters such as mass flow rate, wind speed, atmospheric temperature, inlet fluid temperature, fluid mean temperature and solar intensity were used in input layer, and one variable, the thermal efficiency was used in output layer. Same parameters were used in MLR model. It is observed that GRNN model is the best model due to lowest error and highest value of R2 as compared to MLP, RBF and MLR model performances. It is found that the value of MAE, RMSE and R2 for GRNN model are 1.1128E−03, 5.9284E−06 and 0.99758 respectively, and the model efficiency is 0.99760, which is the highest value as compared to other model. These results confirmed that the GRNN model is appropriate model to predict the thermal performance of solar air heater.

Experimental investigation of thermal performance of parallel connected vortex tubes with various nozzle materials

This paper is about experimental investigation for thermal performance of two identical parallel connected counter flow Ranque-Hilsch vortex tubes by using different orifice nozzle numbers and nozzle materials and also compressed air as a working fluid. The effects of nozzle numbers and materials on thermal performance by applying compressed air at the inlet at different pressures were experimentally determined. Experimental analyses were carried out by using polyamide plastic, aluminum and brass as nozzle materials with inlet pressure range 150–550 kPa with 50 kPa increment. Orifices having 2, 4 and 6 nozzle numbers were used in the vortex tubes. The length – diameter ratios (L/D) of the vortex tubes are 14 and the cold mass fractions are 0.36. The results of experimental studies revealed that the maximum performance was obtained with aluminum nozzles with nozzle number 6 at 550 kPa inlet pressure.

Characterization and modelling of thermal protective performance of fabrics under different levels of radiant-heat exposures

The investigation of thermal protective performance of fabrics is highly relevant in order to procure and further develop the firefighters' protective clothing. Therefore, this paper aims at investigating the thermal protective performance of fabrics used in firefighters' clothing under different levels of radiant-heat exposures. For this, properties of a set of thermal protective single- and multi-layered fabrics were measured, and these fabrics were tested under radiant-heat exposures using the Method B of ISO 6942:2002 standard. During the testing, fabrics were exposed to low (10 kW/m2), medium (40 kW/m2), and high (80 kW/m2) intensity radiant-heat exposures; and the heat transfer level (i.e., time required to increase the skin temperature of a wearer/firefighter by certain degrees) through these fabrics were calculated to measure their thermal protective performance. The effects of fabric parameters, structures, properties, and radiant-heat intensities on the protective performance were characterized, and fabric properties that significantly affected the protective performance were statistically identified at different level of radiant-heat exposures. It has been found that weight, thickness, thermal resistance, and evaporative resistance can positively affect the protective performance. Also, the significant fabric properties affecting the protective performance vary for single- and multi-layered fabrics. By using these significant properties, the protective performance of single- and multi-layered fabrics were also separately predicted by mathematical models, i.e., multiple linear regression models and multiple logarithmic regression models. As per the findings of this study, multiple linear regression models can effectively be used to predict the thermal protective performance of fabrics. This study will lead towards building a better understanding and prediction of thermal protective performance of fabrics under radiant-heat exposures.

Experimental investigation of thermal performance of an evacuated U-Tube solar collector with ZnO/Etylene glycol-pure water nanofluids

Abstract In this paper, the efficiency of an evacuated U-tube solar collector (EUSC) with ZnO/Etylene Glycol-Pure Water (ZnO/EG-PW) as a working fluid was experimentally investigated. 50%–50% EG-PW was used as a base fluid. To prepare the nanofluids ZnO nanoparticles were added to the EG-PW base fluid at different volume concentrations (1.0%, 2.0%, 3.0% and 4.0%). The maximum collector efficiency was obtained at equal working fluid inlet temperature and ambient temperature in all experiments. Moreover, the highest collector efficiency was determined 62.87% for 3.0 vol.% and mass flow rate of 0.045 kg/s that it was 26.42% higher than EG-PW as a working fluid. Also, this value is 5.2% and 6.88% higher than the base fluid for the mass flow rates of 0.03 and 0.02 kg/s, respectively. It was determined also that the thermal conductivity of ZnO/EG-PW nanofluid increases with increasing nanoparticle volume concentration.

Investigation of Thermal Performance of a Solar Pond With External Heat Addition

This study addresses the method of adding heat to a salt gradient solar pond (SGSP) from external sources and investigates the thermal performance of the pond. In this case, the external heat source is solar heat collected by evacuated tube solar collectors (ETSC), and collected heat is transferred to the lower-convective zone (LCZ) of the SGSP by circulating fluid from the LCZ. Results show that heat addition from the external source enhances the thermal performance of the SGSP in terms of heat recovery and thermal efficiency but with certain constraints. The heat addition efficiency reduces with increase in aperture area of the ETSC. Also with increasing heat addition, the heat removal from the SGSP has to be increased; otherwise, the SGSP efficiency reduces rapidly. Heat removal from SGSP has to be performed keeping in mind the heat demand and the quality of heat. The latter reduces with an increase of heat extraction beyond a certain limit. Hence, optimizing the range of parameters in case of adding heat from external sources is very important for the best performance of a SGSP.

Experimental and numerical investigations of thermal performance of a Hemp Lime external building insulation

Hemp-concrete is a green material which has become nowadays highly recommended in the construction field. It finds applications as internal or external thermal insulator in wooden frame walls. At wall scale, studies proved that using Hemp-concrete in building envelope can improve indoor hygrothermal comfort. However, at building scale, hemp-concrete is scarcely studied. In that context, a French building in Grand-Est region, Champagne-Ardennes, employing hemp-concrete as external insulator is selected and studied. An apartment is monitored for several months. Indoor temperatures, relative humidities, thermal heat flux as well as external weather conditions are measured using sensors installed inside the apartment and a weather station at the building roof. Measurements underline the hemp-concrete ability to dampen external weather conditions by showing good results for both indoor temperature and relative humidity. Experimental approach is then coupled with a numerical validation at the wall and room scales using SPARK simulation tool. Investigations are conducted on thermal heat flux through the wall, indoor office air temperature, and relative humidity. Results show a good agreement between numerical values and experimental measurements.

Investigation of thermal performance by applying a solar chimney with PCM towards the natural ventilation of model house under Climate of Thailand

This paper reports experimental investigation of the thermal performance of a new configuration of solar chimney integrating a phase change material (SC-PCM) aimed to enhance natural ventilation and reduce heat gain admission. This SC-PCM is composed of double walls with a 0.05 m air gap between the two. The outer wall exposed to the sun is a triple-layer wall: the first is a black-painted cement board panel 0.01 m thick. The second layer is a tank (0.015 m x 0.8 m x 1.28m) containing or paraffin. The third layer is a zinc sheet 0.005 m thick. The inner wall is a lightweight concrete 0.07 m thick. There are two 0.012 m x 0.80 m openings at the bottom (room side) and on the top of SC-PCM (outside) to allow air circulation and ventilating indoor space. Openings were protected from insects using screens. The SC-PCM was integrated into the south facade of a small house, 4.05 m3 of volume, made from 10 cm thick concrete walls. Thermal performances were compared to a simple concrete wall (SW) using another house model of the same volume. The experimental results revealed that indoor temperature of solar chimney with PCM room was lower than the single concrete wall room. Also SC-PCM induced noticed ventilation rate which varied following the intensity of solar radiation. As a conclusion, this new configuration of solar chimney integrating PCM is quite efficient as it could induce ventilation and reduce heat gain admitted through the south wall considerably. Thus, this SC-PCM can contribute to energy saving and promote sustainable built environment.

Experimental and numerical investigation of thermal radiator performances as a source of heat energy in design of dryer simulation

The purposes of this research was to investigate the temperature performance of tube and fins car radiator experimentally and numerically. The experiment research was carried out on a simulation design consists of a reservoir water tank, a heater, pump to circulate hot water to the radiator and a cooling fan. The hot water mass flow rate is 0.486 kg/s, and the cooling air velocity of the fan is 1 m/s. The heat transfer rate and the effectiveness of radiator were investigated. The results showed that the exhaust heat transfer rate from the radiator tended to increase over time, with an average heat transfer rate of 3974.3 Watt. The maximum heat transfer rate was 4680 Watt obtained at 6 minutes. The effectiveness of the radiator (ε) over time tends to increase with an average of ε = 0.3 and the maximum effectiveness value was obtained at 12 minutes i.e. 0.35. The numerical research conducted using CFD method. The geometry and meshing created using ANSYS Workbench and the post processing using Fluent. The simulation result showed the similarity with the experimental research. The temperatures of air-side radiator are about 45°C.

Investigation of heat transfer in mechanical draft wet cooling towers using infrared thermal images: An experimental study

This article deals with an experimental investigation of thermal performance of mechanical draft wet cooling towers by changing various parameters such as hot water temperature, water flow rate, air mass flow rate and stage numbers of packing. In fact, this research attempts to focus on packing density influences with an emphasis on the role of stage numbers of packing. The results imply that coefficient of efficiency is in direct relation with air mass flow rate, hot water temperature and stage numbers of packing, while it diminishes by increasing the water flow rate. On the other hand, thermal images are provided for visualizing temperature distribution within the studied cooling tower. Afterward, these images are utilized so as to obtain pertinent temperature histograms and also temperature distribution along the vertical and horizontal directions for three packings. Finally, regression analysis is employed in order to derive design equations from the measured data.

Investigation of thermal and hydrodynamic performance of impingement jets solar air passage with protrusion with combination arc obstacle on the heated plate

ABSTRACTIn this article an experimental analysis has been conducted to study the effect obstacle parameters on thermal and hydrodynamic performance of impingement jets solar air passage having protrusion with combined arc obstacles on the heated surface. The study has involved the values of Reynolds number from 4000 to 18000, relative height ratios () from 0.8 to 1.7, relative pitch ratios () from 9.0 to 12, angle of arc () from 40 to 80, stream wise variation () from 0.39 to 0.56, and span wise variation () from 0.82 to 0.99, and jet diameter ratio of 0.065 respectively. Experimental data pertinent to Nusselt number () and friction factor () were generated for various sets of roughness and flow parameters. The highest improvement is obtained at a range of =1.1,=10, =60°, =0.43, =0.86, and 0.065 respectively. The maximum value of the thermal hydrodynamic performance was found to be 1.50 for the range of parameters investigated.