Heat Transfer Analysis for a Small-Size Direct-Flow Coaxial Concentrating Collector

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Fabrizio Alberti ◽  
Luigi Crema ◽  
Alessandro Bozzoli
Keyword(s):  
Heat Transfer ◽  
Focal Point ◽  
Fluid Dynamic ◽  
Hot Water ◽  
Heat Transfer Analysis ◽  
Forced Flow ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Metal Seal ◽  
Thermal Oil

A coaxial evacuated solar tube has been analyzed. The tube is included in a small-scale concentrated solar power (CSP) system, which runs a cogeneration Stirling engine unit. The engine provides electricity and at the same time generates hot water for heating and sanitary purposes, by cooling down the compression cylinder. The present work is focused on the thermodynamic characterization for a forced-flow in the coaxial evacuated tube, which can heat thermal oil up to 300 °C, when coupled with a parabolic trough collector. The single coaxial tube is 2 m long, it has one glass penetration, it is provided with a glass–metal seal and it has an absorber tube in the focal point with a diameter of 12 mm. A model based on heat transfer analysis coupled with fluid dynamic is presented and discussed. The model is then used to investigate spatial temperature profiles and thermal behaviors for the whole solar collector. It improves previous works in the field of concentrating solar collectors and covers the research in small-size concentrating system using thermal oil as heat transfer fluid.

scholarly journals Performance evaluation of nanofluid on parabolic trough solar collector

2020 ◽  
Vol 24 (2 Part A) ◽  
pp. 853-864 ◽  
Author(s):  
Gopalsamy Vijayan ◽  
Karunakaran Rajasekaran
Keyword(s):  
Heat Transfer ◽  
Aluminum Oxide ◽  
Solar Collector ◽  
Focal Point ◽  
Deionized Water ◽  
Hot Water ◽  
Heat Transfer Fluid ◽  
Maximum Efficiency ◽  
Parabolic Trough ◽  
Parabolic Trough Solar Collector

In the present work, the performance of aluminum oxide and deionized water nanofluid used as heat transfer fluid on a parabolic trough solar collector system with hot water generation tank is evaluated. The parabolic trough solar collector is developed using easily and locally accessible materials. Five different concentrations of aluminum oxide and deionized water based nanofluid from 0.5-2.5% is prepared by the magnetic stirrer initially and then the mixture is subjected to ultrasonication process to break aggregates with the absence of surfactant. The prepared nanofluids are allowed to flow through the absorber which is located at a focal point of the solar collector. The performance of nanofluid is compared with pure deionized water. The test is conducted from 8.00 a. m. to 16.00 p. m. daily in the whole length of the test span. The heat transfer fluid is allowed to flow at a mass-flow rate of 0.020 kg/s and 0.09246 m/s velocities. The maximum solar radiation is 821 W/m2, and maximum efficiency is observed at noon time 60.41% for deionized water and 60.49% for 2.5% volumetric fraction of alumina nanofluid. The efficiency enhancement was 3.90% than deionized water. The influence of the critical parameter on the performance is also examined.

scholarly journals Modification of a Solar Thermal Collector to Promote Heat Transfer inside an Evacuated Tube Solar Thermal Absorber

2021 ◽  
Vol 11 (9) ◽  
pp. 4100
Author(s):  
Rasa Supankanok ◽  
Sukanpirom Sriwong ◽  
Phisan Ponpo ◽  
Wei Wu ◽  
Walairat Chandra-ambhorn ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Medium Temperature ◽  
Change Behavior ◽  
Set Up ◽  
Evacuated Tube ◽  
Heating Medium

Evacuated-tube solar collector (ETSC) is developed to achieve high heating medium temperature. Heat transfer fluid contained inside a copper heat pipe directly affects the heating medium temperature. A 10 mol% of ethylene-glycol in water is the heat transfer fluid in this system. The purpose of this study is to modify inner structure of the evacuated tube for promoting heat transfer through aluminum fin to the copper heat pipe by inserting stainless-steel scrubbers in the evacuated tube to increase heat conduction surface area. The experiment is set up to measure the temperature of heat transfer fluid at a heat pipe tip which is a heat exchange area between heat transfer fluid and heating medium. The vapor/ liquid equilibrium (VLE) theory is applied to investigate phase change behavior of the heat transfer fluid. Mathematical model validated with 6 experimental results is set up to investigate the performance of ETSC system and evaluate the feasibility of applying the modified ETSC in small-scale industries. The results indicate that the average temperature of heat transfer fluid in a modified tube increased to 160.32 °C which is higher than a standard tube by approximately 22 °C leading to the increase in its efficiency by 34.96%.

Conjugate Heat Transfer Analysis for Gas Turbine Cooled Stator

2012 ◽  
Author(s):  
Kuo-San Ho ◽  
Christopher Urwiller ◽  
S. Murthy Konan ◽  
Jong S. Liu ◽  
Bruno Aguilar
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Test Data ◽  
Conjugate Heat Transfer ◽  
Fluid Dynamic ◽  
Thermal Analyses ◽  
Convection Heat Transfer ◽  
Heat Transfer Analysis ◽  
Engine Test ◽  
Adiabatic Wall

This paper explores the conjugate heat transfer (CHT) numerical simulation approach to calculate the metal temperature for the gas turbine cooled stator. ANSYS CFX12.1 code was selected to be the computational fluid dynamic (CFD) tool to perform the CHT simulation. The 2-equation RNG k-ε turbulence model with scalable modified wall function was employed. A full engine test with thermocouple measurement was performed and used to validate the CHT results. Metal temperatures calculated with the CHT model were compared to engine test data. The results demonstrated good agreement between test data and airfoil metal temperatures and cooling flow temperatures using the CHT model. However, the CHT calculations in the outer end wall had a discrepancy compared to the measured temperatures, which was due to the fact that the CHT model assumed an adiabatic wall as a boundary condition. This paper presents a process to calculate convection heat transfer coefficient (HTC) for cooling passages and airfoil surfaces using CHT results. This process is possible because local wall heat flux and fluid temperatures are known. This approach assists in calibrating an in-house conduction thermal model for steady state and transient thermal analyses.

scholarly journals Performance Evaluation of a Small-Scale Latent Heat Thermal Energy Storage Unit for Heating Applications Based on a Nanocomposite Organic PCM

2019 ◽  
Vol 3 (4) ◽  
pp. 88 ◽  
Author(s):  
Maria K. Koukou ◽  
George Dogkas ◽  
Michail Gr. Vrachopoulos ◽  
John Konstantaras ◽  
Christos Pagkalos ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Thermal Behavior ◽  
Latent Heat ◽  
Flow Rate ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Transfer Fluid ◽  
Small Scale ◽  
Solidification Processes

A small-scale latent heat thermal energy storage (LHTES) unit for heating applications was studied experimentally using an organic phase change material (PCM). The unit comprised of a tank filled with the PCM, a staggered heat exchanger (HE) for transferring heat from and to the PCM, and a water pump to circulate water as a heat transfer fluid (HTF). The performance of the unit using the commercial organic paraffin A44 was studied in order to understand the thermal behavior of the system and the main parameters that influence heat transfer during the PCM melting and solidification processes. The latter will assist the design of a large-scale unit. The effect of flow rate was studied given that it significantly affects charging (melting) and discharging (solidification) processes. In addition, as organic PCMs have low thermal conductivity, the possible improvement of the PCM’s thermal behavior by means of nanoparticle addition was investigated. The obtained results were promising and showed that the use of graphite-based nanoplatelets improves the PCM thermal behavior. Charging was clearly faster and more efficient, while with the appropriate tuning of the HTF flow rate, an efficient discharging was accomplished.

Heat Transfer Analysis of Human Cell Culture Under RF Exposure

2005 ◽  
Author(s):  
Muhammad Khalid ◽  
Chenn Zhou ◽  
Ashish Bassi ◽  
San Ming Wang ◽  
Howard Gerber ◽  
...  
Keyword(s):  
Gene Expression ◽  
Heat Transfer ◽  
Electric Field ◽  
Fluid Dynamic ◽  
Operating Conditions ◽  
Heat Transfer Analysis ◽  
Heat Shock Gene ◽  
Exposure System ◽  
Finite Element Software ◽  
Rf Exposure

A 2.45 GHz radio frequency (RF) exposure system was designed and used to study the RF effects on the genome-wide gene expression in cultured human cells. In this system, a T-25 culture flask, which contains 10 × 106 cells in a 10ml medium, is placed in a WR 340 waveguide. The waveguide serves as an environmental chamber. The source is a pulsed magnetron for obtaining a high electric field with the specific absorption rate (SAR) at approximately 10 W/kg. In order to ensure the non-thermal effect, the system was designed to maintain a temperature of 37°C. In this research, the heat transfer analysis of the system was conducted using the computational fluid dynamic (CFD) software FLUENT® coupled with the finite element software, High Frequency Structural Simulation (HFSS) by Ansoft. The electric field was first analyzed by using HFSS to calculate the SAR distribution as a heat source input for CFD calculations. The fluid flow and temperature distributions within the flask were then analyzed using FLUENT®. The results were validated experimentally by measuring the temperatures with fluoroptic thermometer probes as well as by examining the level of heat shock gene expression. These results provide useful information for a better understanding and controlling of the operating conditions of the system.

scholarly journals Modeling and Characteristic Analysis of a Solar Parabolic Trough System: Thermal Oil as the Heat Transfer Fluid

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Zhai Rongrong ◽  
Yang Yongping ◽  
Yan Qin ◽  
Zhu Yong
Keyword(s):  
Heat Transfer ◽  
Solar Radiation ◽  
Working Condition ◽  
Heat Transfer Fluid ◽  
System Dynamic Model ◽  
Parabolic Trough ◽  
Characteristic Analysis ◽  
Collector System ◽  
Typical Summer ◽  
Thermal Oil

The thermal oil is applied as the heat transfer fluid in a solar parabolic trough collector system. Firstly, the system dynamic model was established and validated by the real operating data in typical summer and spring days in references. Secondly, the alteration characteristics of different solar radiation, inlet water temperature and flow rate, and collectors’ area and length are analyzed and compared with the normal working condition. The model can be used for studying, system designing, and better understanding of the performance of parabolic trough systems.

Hot Water Immersion To Eliminate Escherichia coli O157:H7 on the Surface of Whole Apples: Thermal Effects and Efficacy

2001 ◽  
Vol 64 (4) ◽  
pp. 451-455 ◽  
Author(s):  
G. J. FLEISCHMAN ◽  
C. BATOR ◽  
R. MERKER ◽  
S. E. KELLER
Keyword(s):  
Heat Transfer ◽  
Escherichia Coli ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Water Immersion ◽  
Hot Water ◽  
Heat Transfer Analysis ◽  
Escherichia Coli O157 ◽  
Transfer Coefficients ◽  
Hot Water Immersion

The effect of hot water immersion on both the reduction of Escherichia coli O157:H7 on the apple surface and internal temperatures of the apple was assessed in this study. Microbial reductions were measured experimentally, whereas internal temperatures were calculated through a mathematical analysis of experimental heat transfer data obtained from the apples. A method was developed to provide a purely surface-based inoculation of E. coli O157:H7. Rinsing produced no reduction, and treatments at 80 and 95°C produced reductions of more than 5 logs in 15 s or less. The heat transfer analysis based on experimental data was used to calculate surface heat transfer coefficients and predict temperatures throughout the apple. The analysis indicated a low heat transfer rate. Although it reduces thermal degradation, a low heat transfer rate precludes thermal-based reduction of any internalized microorganisms.

scholarly journals A Multi-Fidelity Aero-Thermal Design Approach for Secondary Air Systems

2020 ◽  
Author(s):  
Dario Amirante ◽  
Nicholas J. Hills ◽  
Paolo Adami
Keyword(s):  
Heat Transfer ◽  
Thermal Design ◽  
Rotor Blades ◽  
Computational Method ◽  
Heat Transfer Analysis ◽  
Heat Transfer Fluid ◽  
Navier Stokes ◽  
Fluid Interfaces ◽  
Coupling Strategy ◽  
Secondary Air

Abstract The paper presents a multi-disciplinary approach for aero-thermal and heat transfer analysis for internal flows. The versatility and potential benefit offered by the approach is described through the application to a realistic low pressure turbine assembly. The computational method is based on a run time code-coupling architecture that allows mixed models and simulations to be integrated together for the prediction of the sub-system aero-thermal performance. In this specific application the model is consisting of two rotor blades, the embedded vanes, the inter-stage cavity and the solid parts. The geometry represents a real engine situation. The key element of the approach is the use of a fully modular coupling strategy that aims to combine (1) flexibility for design needs, (2) variable level of modelling for better accuracy and (3) in memory code coupling for preserving computational efficiency in large system and sub-system simulations. For this particular example Reynolds Averaged Navier-Stokes (RANS) equations are solved for the fluid regions and thermal coupling is enforced with the metal (conjugate heat transfer). Fluid-fluid interfaces use mixing planes between the rotating parts while overlapping regions are exploited to link the cavity flow to the main annulus flow as well as in the cavity itself for mapping of the metal parts and leakages. Metal temperatures predicted by the simulation are compared to those retrieved from a thermal model of the engine, and the results are discussed with reference to the underlying flow physics.

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