Heat Loss Characteristics of a Roof Integrated Solar Micro-Concentrating Collector

2011 ◽  
Author(s):  
Tanzeen Sultana ◽  
Graham L. Morrison ◽  
Siddarth Bhardwaj ◽  
Gary Rosengarten
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Large Scale ◽  
Radiation Heat Transfer ◽  
Industrial Process ◽  
Hot Water ◽  
Solar Thermal ◽  
Convection Heat ◽  
Thermal Systems ◽  
Optical Efficiency

Concentrating solar thermal systems offer a promising method for large scale solar energy collection. It is feasible to use concentrating solar thermal systems for rooftop applications such as domestic hot water, industrial process heat and solar air conditioning for commercial, industrial and institutional buildings. This paper describes the thermal performance of a new low-cost solar thermal micro-concentrating collector (MCT), which uses linear Fresnel reflector technology and is designed to operate at temperatures up to 220°C. The modules of this collector system are approximately 3 meters long by 1 meter wide and 0.3 meters high. The objective of the study is to optimize the design to maximise the overall thermal efficiency. The absorber is contained in a sealed enclosure to minimise convective losses. The main heat losses are due to natural convection inside the enclosure and radiation heat transfer from the absorber tube. In this paper we present the results of a computational investigation of radiation and convection heat transfer in order to understand the heat loss mechanisms. A computational model for the prototype collector has been developed using ANSYS-CFX, a commercial computational fluid dynamics software package. Radiation and convection heat loss has been investigated as a function of absorber temperature. Preliminary ray trace simulation has been performed using SolTRACE and optical efficiency has been evaluated. Finally, the MCT collector efficiency is also evaluated.

scholarly journals Study on Sewage Sludge Drying System With Built-in Solar Drying Bed

2021 ◽  
Vol 237 ◽  
pp. 01041
Author(s):  
Zhipan Gu ◽  
Jichun Yang ◽  
Jing Liu ◽  
Leren Tao ◽  
Ye Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Sewage Sludge ◽  
Radiation Heat Transfer ◽  
Middle Layer ◽  
Bottom Layer ◽  
Mass Transfer Process ◽  
Hot Water ◽  
Solar Drying ◽  
Hot Air ◽  
Air Supply

In this paper, the renewable energy solar energy is used as the heat source. The combination of solar drying bed and traditional hot air drying can effectively reduce energy consumption and operation cost. The drying chamber is divided into three layers. The top air supply outlet supplies hot air, the middle layer places wet sludge, and the bottom layer uses hot water coil to dry the sludge. The whole drying process is a heat and mass transfer process with convective heat transfer and radiation heat transfer. After analysis and comparison with traditional energy drying, it is found that drying 97.5kg of sewage sludge will save 79% energy, save 12.84 kg of standard coal, reduce 32 kg of carbon dioxide and 1.284 kg of sulphur dioxide.

scholarly journals Aplicaciones del Captador Solar de Placa Plana y del Captador de Tubo de Vacío en la Edificación = Applications of the Flat Plate Solar Collectors and the Vacuum Tube Solar Collectors in Building

2018 ◽  
Vol 4 (3) ◽  
pp. 25 ◽  
Author(s):  
Daniel Ferrández ◽  
Carlos Moron ◽  
Jorge Pablo Díaz ◽  
Pablo Saiz
Keyword(s):  
Flat Plate ◽  
Solar Collector ◽  
Energy Demand ◽  
Hot Water ◽  
Solar Thermal ◽  
Solar Collectors ◽  
Thermal Systems ◽  
Vacuum Tube ◽  
Solar Thermal Collectors ◽  
Flat Plate Solar Collector

ResumenEl actual Código Técnico de la Edificación (CTE) pone de manifiesto la necesidad de cubrir parte de la demanda energética requerida para el abastecimiento de agua caliente sanitaria y climatización de piscinas cubiertas mediante sistemas de aprovechamiento de la energía solar térmica. En este artículo se presenta una comparativa entre las dos principales tipologías de captadores solares térmicos que existen en el mercado: el captador de placa plana y el captador de tubo de vacío, atendiendo a criterios de fracción solar, diseño e integración arquitectónica. Todo ello a fin de discernir en qué circunstancias es más favorable el uso de uno u otro sistema, comparando los resultados obtenidos mediante programas de simulación con la toma de medidas in situ.AbstractThe current Technical Building Code (CTE) highlights the need to cover part of the energy demand required for the supply of hot water and heating of indoor swimming pools using solar thermal systems. This article presents a comparison between the two main types of solar thermal collectors that exist in the market: the flat plate solar collector and the vacuum tube solar collector, according to criteria of solar fraction, design and architectural integration. All of this in order to discern in what circumstances the use of one or the other system is more favourable, comparing the results obtained through simulation programs with the taking of measurements in situ.

Numerical Analysis of Convection Heat Transfer for Subsea Xmas Tree Assembly

2012 ◽  
Author(s):  
Kuang Ding ◽  
Hongwu Zhu ◽  
Jinya Zhang ◽  
Xuan Luo ◽  
Junyao Zhu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Heat Loss ◽  
Convective Heat ◽  
Structural Reliability ◽  
Sea Water ◽  
Convective Heat Transfer Coefficient ◽  
Convection Heat Transfer ◽  
Water Velocity ◽  
Convection Heat

This study aims to investigate the convection heat transfer of a horizontal subsea Xmas tree assembly at a high spatial resolution. Such study is important for increasing the structural reliability design and flow assurance level of subsea Xmas tree. Computational fluid dynamics (steady Reynolds-averaged Navier-Stokes) is adopted to evaluate the forced convective heat transfer of the subsea Xmas tree assembly. The temperature, the convection heat loss and the convective heat transfer coefficient (CHTC) at the surfaces of the subsea Xmas tree assembly are numerically obtained with low-Reynolds number modeling (LRNM). The numerical results show that the outer surface temperatures of the subsea tree are close to that of the ambient cold sea water with the exception of the pipeline. The components along the internal production tubes are typical “hot spots,” which have high CHTHs and cause a great deal of heat loss. Under the designed water depth, the effects of installation orientation and sea water velocity on convective heat transfer are investigated. The overall average CHTCs and the local CHTC distribution of the subsea Xmas tree assembly are depended on the installation orientation. Meanwhile, with the increase of the sea water velocity, the growth rates of the CHTCs for individual components show great difference. Ultimately, for selected installation orientation, the CHTC-sea water velocity correlation is derived by using a power-law CHTC-Uin correlation.

Real Time Experimental Performance Assessment of a Photovoltaic Thermal System Cascaded with Flat Plate and Heat Pipe Evacuated Tube Collector

2021 ◽  
pp. 1-28
Author(s):  
Laveet Kumar ◽  
Md Hasanuzzaman ◽  
Nasrudin Abd Rahim
Keyword(s):  
Performance Assessment ◽  
Flat Plate ◽  
Heat Pipe ◽  
Large Scale ◽  
Industrial Process ◽  
Simulation Models ◽  
Solar Thermal ◽  
Evacuated Tube Collector ◽  
Flat Plate Collector ◽  
Evacuated Tube

Abstract In response to the global quest for a sustainable and environmentally friendly source of energy most scientists' discretion is solar energy, especially solar thermal. However, successful deployment of solar thermal technologies such as solar assisted process heating (SAPH) systems in medium- to large-scale industries is still in quandary due to their inefficacy in raising ample temperatures. Cascaded SAPH system, which is essentially a series combination of two same or different types of thermal collectors, may provide a worthwhile solution to this problem. In this article, performance assessment and comparison of two cascaded SAPH systems have been presented: photovoltaic thermal (PVT) cascaded with flat-plate collector (PVT-FPC) and PVT coupled with heat-pipe evacuated tube collector (PVT-HPETC). Simulation models have been presented for individual FPC, HPETC and PVT as well as PVT cascaded with FPC and HPETC systems in TRNSYS and validated through outdoor experimentation. Both the first and the second laws of thermodynamics have been employed to reveal veritable performance of the systems. Results show that PVT-HPETC delivers better performance with 1625 W thermal energy, 81% energy efficiency and 13.22% exergy efficiency. It cuts 1.37 kg of CO2 on an hourly basis. Cascaded systems can be effective in sustaining industrial process heat requirements.

A review on the application of photovoltaic thermal systems for building façades

2019 ◽  
Vol 41 (1) ◽  
pp. 86-107 ◽  
Author(s):  
Ahmad Riaz ◽  
Ruobing Liang ◽  
Chao Zhou ◽  
Jili Zhang
Keyword(s):  
Thermal Energy ◽  
Large Scale ◽  
Electrical Energy ◽  
Building Envelope ◽  
Hot Water ◽  
Working Fluid ◽  
Thermal Systems ◽  
Air Supply ◽  
Building Facades ◽  
Photovoltaic Thermal System

The hybrid photovoltaic-thermal system has shown great progress. Electrical energy is produced from PV panels while thermal energy is produced via a working fluid carried through the panels. In this paper, the vertical PV/T is introduced using working fluids such as air and liquid, which serve to control the excess temperature of the PV panels as well as to collect heat to be made available as thermal energy. Installations of PV/T systems on building façades, as well as integration with other technologies such as heat pipe and heat pump are also discussed. Current studies of such building integration technologies are also explored, including the scale of application. This study aims to provide constructive information which can be used in future development of building facades for large-scale applications, to contribute to future sustainable development. Practical application: This study helps researchers and engineers who are considering photovoltaic thermal systems for building façades to have better understanding of its effect on electrical and thermal energy – for space heating, fresh air supply and hot water supply – using an active building envelope.

Performance Optimization and Parametric Analysis of a Class of Solar-Driven Heat Engines

2010 ◽  
Author(s):  
Houcheng Zhang ◽  
Lanmei Wu ◽  
Guoxing Lin
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Performance Optimization ◽  
Solar Collector ◽  
Heat Engine ◽  
Working Fluid ◽  
Convection Heat ◽  
Combined System ◽  
Heat Engines ◽  
Internal Irreversibility

A class of solar-driven heat engines is modeled as a combined system consisting of a solar collector and a unified heat engine, in which muti-irreversibilities including not only the finite rate heat transfer and the internal irreversibility, but also radiation-convection heat loss from the solar collector to the ambience are taken into account. The maximum overall efficiency of the system, the optimal operating temperature of the solar collector, the optimal temperatures of the working fluid and the optimal ratio of heat transfer areas are calculated by using numerical calculation method. The influences of radiation-convection heat loss of the collector and internal irreversibility on the cyclic performances of the solar-driven heat engine system are revealed. The results obtained in the present paper are more general than those in literature and the performance characteristics of several solar-driven heat engines such as Carnot, Brayton, Braysson and so on can be directly derived from them.

Numerical analysis of a hybrid tubular and cavity air receiver for solar thermal applications

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sayuj Sasidharan ◽  
Pradip Dutta
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Numerical Analysis ◽  
Heat Loss ◽  
Solar Thermal ◽  
Heat Transfer Analysis ◽  
Receiver Design ◽  
Radiation Emission ◽  
Content Type ◽  
Thermal Receiver

Purpose This paper aims to deal with characterisation of the thermal performance of a hybrid tubular and cavity solar thermal receiver. Design/methodology/approach The coupled optical-flow-thermal analysis is carried out on the proposed receiver design. Modelling is performed in two and three dimensions for estimating heat loss by natural convection for an upward-facing cavity. Heat loss obtained in two dimensions by solving coupled continuity, momentum and energy equation inside the cavity domain is compared with the loss obtained using an established Nusselt number correlation for realistic receiver performance prediction. Findings It is found that radiation emission from a heated cavity wall to the ambient is the dominant mode of heat loss from the receiver. The findings recommend that fluid flow path must be designed adjacent to the surface exposed to irradiation of concentrated flux to limit conduction heat loss. Research limitations/implications On-sun experimental tests need to be performed to validate the numerical study. Practical implications Numerical analysis of receivers provides guidelines for effective and efficient solar thermal receiver design. Social implications Pressurised air receivers designed from this method can be integrated with Brayton cycles using air or supercritical carbon-dioxide to run a turbine generating electricity using a solar heat source. Originality/value The present paper proposes a novel method for coupling the flux map from ray-tracing analysis and using it as a heat flux boundary condition for performing coupled flow and heat transfer analysis. This is achieved using affine transformation implemented using extrusion coupling tool from COMSOL Multiphysics software package. Cavity surface natural convection heat transfer coefficient is obtained locally based on the surface temperature distribution.

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