scholarly journals Computational analysis of transient turbulent flow and conjugate heat transfer characteristics in a solar collector panel with internal, rectangular fins and baffles

2010 ◽  
Vol 14 (1) ◽  
pp. 221-234 ◽  
Author(s):  
Rachid Saim ◽  
Said Abboudi ◽  
Boumédiene Benyoucef
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Computational Analysis ◽  
Heat Transfer Characteristics ◽  
Thermal Exchange

The poor thermal exchange between the absorber and the fluid in the solar air flat plate collector, gives the bad performance and the mediocre thermal efficiency. The introduction of obstacles in the dynamic air vein of the solar collector in order to obtain a turbulent flow is a technique that improves the thermal exchange by convection between the air and the absorber. This article present a computational analysis on the turbulent flow and heat transfer in solar air collector with rectangular plate fins absorber and baffles which are arranged on the bottom and top channel walls in a periodically staggered way. To this end we solved numerically, by the finite volumes method, the conservation equations of mass, momentum and energy. The low Reynolds number k-? model was adopted for the taking into account of turbulence. The velocity and pressure terms of momentum equations are solved by the SIMPLE algorithm. The parameters studied include the entrance mass flow rate of air. The influence of the mass flow rate of air on the axial velocity and the efficiency of upward type baffled solar air heaters have been investigated numerically. The results show that the flow and the heat transfer characteristics are strongly dependent on mass-flow rate of air and the presence and/or the absence of the baffles and fins in the solar collector. It was observed that increasing the Reynolds number will increase the efficiency of the solar panel, as expected.

scholarly journals Effect of nanofluid properties and mass-flow rate on heat transfer of parabolic-trough concentrating solar system

2019 ◽  
Vol 16 (1) ◽  
pp. 33-44 ◽  
Author(s):  
M.K. Islam ◽  
Md. Hasanuzzaman ◽  
N.A. Rahim ◽  
A. Nahar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Laminar Flow ◽  
Turbulent Flow ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Parabolic Trough ◽  
Concentrated Solar Energy

Sustainable power generation, energy security, and global warming are the big challenges to the world today. These issues may be addressed through the increased usage of renewable energy resources and concentrated solar energy can play a vital role in this regard. The performance of a parabolic-trough collector’s receiver is here investigated analytically and experimentally using water based and therminol-VP1based CuO, ZnO, Al2O3, TiO2, Cu, Al, and SiC nanofluids. The receiver size has been optimized by a simulation program written in MATLAB. Thus, numerical results have been validated by experimental outcomes under same conditions using the same nanofluids. Increased volumetric concentrations of nanoparticle is found to enhance heat transfer, with heat transfer coefficient the maximum in W-Cu and VP1-SiC, the minimum in W-TiO2 and VP1-ZnO at 0.8 kg/s flow rate. Changing the mass flow rate also affects heat transfer coefficient. It has been observed that heat transfer coefficient reaches its maximum of 23.30% with SiC-water and 23.51% with VP1-SiC when mass-flow rate is increased in laminar flow. Heat transfer enhancement drops during transitions of flow from laminar to turbulent. The maximum heat transfer enhancements of 9.49% and 10.14% were achieved with Cu-water and VP1-SiC nanofluids during turbulent flow. The heat transfer enhancements of nanofluids seem to remain constant when compared with base fluids during either laminar flow or turbulent flow.

Influence of Dimensionless Parameter on De-Ionized Water-alumina Nanofluid Based Parabolic Trough Solar Collector

2020 ◽  
Vol 13 (3) ◽  
pp. 206-221
Author(s):  
Vijayan Gopalsamy ◽  
Karunakaran Rajasekaran ◽  
Logesh Kamaraj ◽  
Siva Sivasaravanan ◽  
Metin Kok
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
Solar Collector ◽  
Dimensionless Parameter ◽  
Parabolic Trough ◽  
Alumina Nanofluid ◽  
Parabolic Trough Solar Collector

Background: Aqueous-alumina nanofluid was prepared using magnetic stirrer and ultrasonication process. Then, the prepared nanofluid was subjected to flow through the unshielded receiver of the parabolic trough solar collector to investigate the performance of the nanofluid and the effects of the dimensionless parameter were determined. Methods: The experimental work has been divided into two sections. First, the nanofluid was prepared and tested for its morphology, dimensions, and sedimentation using X-Ray Diffraction and Raman shift method. Then, the nanofluids of various concentrations from 0 to 4.0% are used as heat transfer fluid in unshielded type collector. Finally, the effect of the dimensionless parameter on the performance was determined. Results: For the whole test period, depending upon the bulk mean temperature, the dimensionless parameters such as Re and Nu varied from 1098 to 4552 & 19.30 to 46.40 for air and 2150 to 7551 & 11.11 to 48.54 for nanofluid. The enhancement of thermal efficiency found for 0% and 4.0% nanoparticle concentrations was 32.84% for the mass flow rate of 0.02 kg/s and 13.26% for the mass flow rate of 0.06 kg/s. Conclusion: Re and Nu of air depend on air velocity and ambient temperature. Re increased with the mass flow rate and decreased with concentration. Heat loss occurred by convection mode of heat transfer. Heat transfer coefficient and global efficiency increased with increased mass flow rate and volume fraction. The thermal efficiency of both 0% and 4.0% concentrations became equal for increased mass flow rate. It has been proven that at high mass flow rates, the time available to absorb the heat energy from the receiver is insufficient.

scholarly journals Experimental Investigation on Triple Concentric Tube Heat Exchanger with Helical Baffles

2020 ◽  
Vol 6 (11) ◽  
pp. 14-20
Author(s):  
Rohit Kumar Gaur ◽  
Dr. Shashi Kumar Jain ◽  
Dr. Sukul Lomash
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Exchanger ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Exchangers ◽  
Solid Particles ◽  
Tube Heat Exchanger ◽  
High Heat Transfer

A heat exchanger is a device used to transfer thermal energy between two or more liquids, between a solid surface and a liquid, or between solid particles and a liquid at different temperatures and in thermal contact where shell and tube heat exchangers contain a large number of tubes packed in a jacket whose axes are parallel to those of the shell. Heat transfer occurs when one fluid flows into the pipes while the other flows out of the pipes through the jacket. In industry, three-tube heat exchanger tubes are used as condensers, evaporators, sub cooler, heat recovery heat exchangers, etc. The three concentric tube heat exchanger is a constructively modified version of the double concentric tube heat exchanger as an intermediate tube adds some advantages over the double tube heat exchangers in that it is larger tube surface area heat transfer per unit of length.  In the present study, the triple tube heat exchanger is further modified by inserting helical baffle over the surface of one of the tubes and observed turbulence flow which may lead to high heat transfer rates between the fluids of heat exchanger. Further, the Reynolds number, Nusselt number, friction factor of the flow at different mass flow rates of the hot fluid while keeping a constant mass flow rate of cold and normal temperature fluids were calculated. It was found that as the mass flow rate of the fluid increases the Reynolds number increases, the turbulence in the flow will increase which will cause the intermixing of the fluid, higher the rate of intermixing, more will be the heat transfer of the system.  

Thermodynamic Performance Evaluation of a Solar Parabolic Dish Assisted Multigeneration System

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Muhammad Abid ◽  
Muhammad Sajid Khan ◽  
Tahir Abdul Hussain Ratlamwala
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Integrated System ◽  
Heat Transfer Fluid ◽  
Outlet Temperature ◽  
Parabolic Dish ◽  
Single Effect

The concentration ratio of the parabolic dish solar collector (PDSC) is considered to be one of the highest among the concentrated solar power technologies (CSPs); therefore, such system is capable of generating more heat rate. The present paper focuses on the integration of the PDSC with the combined cycle (gas cycle as the toping cycle and steam cycle as the bottoming cycle) along with the utilization of waste heat from the power cycle to drive the single effect lithium bromide/water absorption cycle. Molten salt is used as a heat transfer fluid in the solar collector. The engineering equation solver (EES) is employed for the mathematical modeling and simulation of the solar integrated system. The various operating parameters (beam radiation, inlet and ambient temperatures of heat transfer fluid, mass flow rate of heat transfer fluid, evaporator temperature, and generator temperature) are varied to analyze their influence on the performance parameters (power output, overall energetic and exergetic efficiencies, outlet temperature of the receiver, and as coefficient of performance (COP) and exergy efficiencies) of the integrated system. The results show that the overall energy and exergy efficiencies are observed to be 39.9% and 42.95% at ambient temperature of 27 °C and solar irradiance of 1000 W/m2. The outlet temperature of the receiver is noticed to decrease from 1008 K to 528 K for an increase in the mass flow rate from 0.01 to 0.05 kg/s. The efficiency rate of the power plant is 38%, whereas COP of single effect absorption system is 0.84, and it will decrease from 0.87 to 0.79. However, the evaporator load is decreased to approximately 9.7% by increasing the generator temperature from 47 °C to 107 °C.

Numerical Analysis of Heat Transfer Characteristics of a Falling Film Type Plate-Fin Condenser/Reboiler

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Yuanyuan Zhou ◽  
Jianlin Yu
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Falling Film ◽  
Heat Transfer Characteristics ◽  
Allocation Ratio

Falling film type condensers/reboilers applied to cryogenic air separation units (ASUs) have drawn more attentions in recent years. This paper presents and analyzes a mathematical model for the falling film plate-fin condensers/reboilers (FPCR). In the modeling, both the laminar falling film evaporation and condensation processes, incorporating with interference of mass transfer and interfacial shear stress, are considered, and related to a plate-fin heat exchanger (PHX). The liquid film flow and heat transfer characteristics of oxygen and nitrogen fluids in the PHX are analyzed under given conditions by solving the model with a numerical iteration method. The variations of liquid film thicknesses and local heat transfer coefficients of oxygen and nitrogen as well as the total local heat transfer coefficient have been obtained. Furthermore, the effects of the inlet mass flow rate allocation ratio (i.e., the ratio of inlet mass flow rate of oxygen liquid over the base plate to that over the fin surfaces) on the wetted length of the heat transfer surfaces, the heat transfer performance, and the oxygen liquid circulation ratio (i.e., the ratio of the inlet liquid mass flow rate to the generated vapor mass flow rate) are also discussed. A proper inlet mass flow rate allocation ratio of oxygen liquid is presented. The wave effects are further considered and analyzed through the inclusion of a model for the wave factor.

scholarly journals The Effects of Gravity on the Pressure Drop and Heat Transfer Characteristics of Steam in Microchannels: An Experimental Study

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3575 ◽  
Author(s):  
Minhhung Doan ◽  
Thanhtrung Dang ◽  
Xuanvien Nguyen
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Pressure Drop ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Performance Index ◽  
Gravitational Acceleration ◽  
Heat Transfer Characteristics ◽  
Vertical Microchannel

Experiments were carried out to investigate the pressure drop and heat transfer behaviors of a microchannel condenser. The effects of gravity on the condensation of steam in the microchannels were investigated for both horizontal and vertical cases. For the experimental results, the pressure drop of vertical microchannels in the condenser is lower than for horizontal microchannels. In the case of the horizontal microchannel, as the mass flow rate of steam increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 1.5 kPa to 50 kPa, respectively. While the mass flow rate of steam in the vertical microchannel case increases from 0.01 g·s−1 to 0.06 g·s−1, the pressure drop increases from 2.0 kPa to 44 kPa, respectively. This clearly indicates that the gravitational acceleration affects the pressure drop. The pressure drop of the vertical microchannel is lower than that obtained from the horizontal microchannel. In addition, the capacity of the condenser is the same in both cases. This leads to the performance index obtained from the vertical microchannel condenser being higher than that obtained from the horizontal microchannel condenser. These results are important contributions to the research on the condensation of steam in microchannels.

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