A Parametric Investigation of a Concentrating Photovoltaic/Thermal System With Spectral Filtering Utilizing a Two-Dimensional Heat Transfer Model

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Nick Brekke ◽  
Todd Otanicar ◽  
Drew DeJarnette ◽  
Parameswar Hari
Keyword(s):  
Heat Transfer ◽  
Optical Filter ◽  
Heat Transfer Model ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Transfer Model ◽  
Cell Efficiency ◽  
Photovoltaic Thermal System ◽  
Pv Cell ◽  
The Impact

A 2D heat transfer model of a hybrid photovoltaic/thermal (PV/T) system has been created. This paper investigates the impact of ideal filters to best accommodate for a nonuniform PV temperature along the length of the receiver. The proposed configuration consists of a GaAs cell laminated to an aluminum extrusion. The working fluid, a transparent high-temperature heat transfer fluid with suspended nanoparticles, flows through the hollow extrusion where it cools the PV cell before it is redirected in front of the cell acting as an optical filter. The model accounts for PV cell efficiency, temperature, and bandgap dependence, the details often neglected in prior works.

Parametric Investigation of Concentrating PV/T System With Spectral Filtering Utilizing a 2-D Model

2015 ◽  
Author(s):  
Nick Brekke ◽  
Todd Otanicar ◽  
Drew DeJarnette ◽  
Parameswar Harikumar
Keyword(s):  
Optical Filter ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Spectral Filtering ◽  
Temperature Variations ◽  
Cell Efficiency ◽  
Pv Cell ◽  
D Model ◽  
T System

Hybrid photovoltaic/thermal (PV/T) systems are continually being investigated, in particular the use of such systems in concentrating collectors as part of the ARPA-E FOCUS program. While many combined thermal and electrical models exist, most are limited to 0-D energy balance approaches or 1-D approaches where temperature variations through insulation, glazing and substrates are considered. Here, we develop a 2-D model for a concentrating PV/T system where the model accounts for temperature variations along the length of the collector. The proposed configuration consists of a GaAs cell laminated to an aluminum extrusion. The working fluid, a transparent high temperature heat transfer fluid with suspended nanoparticles, flows through the extrusion where it actively cools the PV cell before passing in front of the cell acting as an optical filter. The model includes PV cell efficiency, temperature, and bandgap dependence, a detail often neglected in prior works. This paper focuses on PV efficiency along the length of the system and outlet fluid temperature for both counter and parallel flow arrangements. Of particular interest here is the wavelength used in the design of the fluid filter and how changing the design impacts the exergetic efficiency and percent of exergy created as heat.

scholarly journals Fast three-dimensional heat transfer model for computing internal temperatures in the bearing housing of automotive turbochargers

2018 ◽  
Vol 21 (8) ◽  
pp. 1286-1297 ◽  
Author(s):  
Antonio Gil ◽  
Andrés Omar Tiseira ◽  
Luis Miguel García-Cuevas ◽  
Tatiana Rodríguez Usaquén ◽  
Guillaume Mijotte
Keyword(s):  
Heat Transfer ◽  
Coke Formation ◽  
Three Dimensional ◽  
Heat Transfer Model ◽  
Operating Conditions ◽  
Thermal Design ◽  
Working Fluid ◽  
Transfer Model ◽  
Lumped Model ◽  
Bearing System

Each of the elements that make up the turbocharger has been gradually improved. In order to ensure that the system does not experience any mechanical failures or loss of efficiency, it is important to study which engine-operating conditions could produce the highest failing rate. Common failing conditions in turbochargers are mostly achieved due to oil contamination and high temperatures in the bearing system. Thermal management becomes increasingly important for the required engine performance. Therefore, it has become necessary to have accurate temperature and heat transfer models. Most thermal design and analysis codes need data for validation; often the data available fall outside the range of conditions the engine experiences in reality leading to the need to interpolate and extrapolate disproportionately. This article presents a fast three-dimensional heat transfer model for computing internal temperatures in the central housing for non-water cooled turbochargers and its direct validation with experimental data at different engine-operating conditions of speed and load. The presented model allows a detailed study of the temperature rise of the central housing, lubrication channels, and maximum level of temperature at different points of the bearing system of an automotive turbocharger. It will let to evaluate thermal damage done to the system itself and influences on the working fluid temperatures, which leads to oil coke formation that can affect the performance of the engine. Thermal heat transfer properties obtained from this model can be used to feed and improve a radial lumped model of heat transfer that predicts only local internal temperatures. Model validation is illustrated, and finally, the main results are discussed.

Geothermal Power Cycle Analysis for Commercial Applicability Using Sequestered Supercritical CO2 as a Heat Transfer or Working Fluid

2011 ◽  
Author(s):  
Brian Janke ◽  
Thomas Kuehn
Keyword(s):  
Heat Transfer ◽  
Binary System ◽  
Power Plants ◽  
Power Production ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Direct System ◽  
Geothermal Power ◽  
The Impact

Thermodynamic analysis has been conducted for geothermal power cycles using a portion of deep ground sequestered CO2 as the working fluid. This allows energy production from much shallower depths and in geologic areas with much lower temperature gradients than those of current geothermal systems. Two different system designs were analyzed for power production with varying reservoir parameters, including reservoir depth, temperature, and CO2 mass flow rate. The first design is a direct single-loop system with the CO2 run directly through the turbine. This system was found to provide higher system efficiency and power production, however design complications such as the need for high pressure turbines, two-phase flow through the turbine and the potential for water-CO2 brine mixtures, could require the use of numerous custom components, driving up the cost. The second design is a binary system using CO2 as the heat transfer fluid to supply thermal energy to an Organic Rankine Cycle (ORC). While this system was found to have slightly less power production and efficiency than the direct system, it significantly reduces the impact of design complications associated with the direct system. This in turn reduces the necessity for certain custom components, thereby reducing system cost. While performance of these two systems is largely dependent on location and operating conditions, the binary system is likely applicable to a larger number of sites and will be more cost effective when used in combination with current off-the-shelf ORC power plants.

scholarly journals A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

2020 ◽  
pp. 146808742092158
Author(s):  
Alberto Broatch ◽  
Pablo Olmeda ◽  
Xandra Margot ◽  
Josep Gomez-Soriano
Keyword(s):  
Heat Transfer ◽  
Combustion Engine ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Insulation Material ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Dimensional Modeling ◽  
The One ◽  
The Impact

This article presents a study of the impact on engine efficiency of the heat loss reduction due to in-cylinder coating insulation. A numerical methodology based on one-dimensional heat transfer model is developed. Since there is no analytic solution for engines, the one-dimensional model was validated with the results of a simple “equivalent” problem, and then applied to different engine boundary conditions. Later on, the analysis of the effect of different coating properties on the heat transfer using the simplified one-dimensional heat transfer model is performed. After that, the model is coupled with a complete virtual engine that includes both thermodynamic and thermal modeling. Next, the thermal flows across the cylinder parts coated with the insulation material (piston and cylinder head) are predicted and the effect of the coating on engine indicated efficiency is analyzed in detail. The results show the gain limits, in terms of engine efficiency, that may be obtained with advanced coating solutions.

The Experimental and Theoretical Evaluation of an Indirect Cooling System for Machining

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Jay C. Rozzi ◽  
John K. Sanders ◽  
Weibo Chen
Keyword(s):  
Heat Transfer ◽  
Tool Life ◽  
Cutting Tool ◽  
Cooling System ◽  
Heat Transfer Model ◽  
Machining Process ◽  
Working Fluid ◽  
Transfer Model ◽  
Cutting Fluids ◽  
Maximum Heat

Cutting fluids have been used in machining processes for many years to decrease the temperature during machining by spraying the coolant into the machining zone directly on the cutting tool and the part. This has the effect of decreasing the tool temperature, which increases tool life and improves the part quality. These benefits come with significant drawbacks. Cutting fluids are environmentally unfriendly, costly, and potentially toxic. An alternative that has been evaluated in this paper is an internal cooling system (ICS) for lathe turning, which cools the cutting tool using a very small amount of an inert, cryogenic working fluid routed through a microchannel heat exchanger (MHX) that is mounted beneath the cutting tool insert. The working fluid absorbs the heat generated during the machining process after which it is harmlessly vented to the environment. This indirect cooling technique results in an environmentally friendly machining process that uses no cutting fluids, enables increased processing speed, and reduces manufacturing costs. An approximate heat transfer model was developed and used to predict the tool life as a function of the tool cooling approach for various speeds. Machining experiments were completed to validate the heat transfer model and confirm that the ICS can significantly improve tool life relative to conventional flood cooling. The validated model was then used to evaluate alternative cooling approaches using the ICS. It was found that the use of a cryogenic working fluid can significantly improve tool life at all cutting speeds but that the latent heat capacity of the working fluid should exceed the expected maximum heat transfer rate into the tool. This work established that the ICS approach is an effective means to increase tool life without the disadvantages associated with external cryogenic cooling methods.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

Theoretical Post-Dryout Heat Transfer Model

2018 ◽  
Vol 1 (1) ◽  
pp. 142-150
Author(s):  
Murat Tunc ◽  
Ayse Nur Esen ◽  
Doruk Sen ◽  
Ahmet Karakas
Keyword(s):  
Heat Transfer ◽  
Droplet Diameter ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Operating Pressure ◽  
Vertical Pipe ◽  
Two Phase ◽  
Experimental Values ◽  
Reactor Operating ◽  
Coolant System

A theoretical post-dryout heat transfer model is developed for two-phase dispersed flow, one-dimensional vertical pipe in a post-CHF regime. Because of the presence of average droplet diameter lower bound in a two-phase sparse flow. Droplet diameter is also calculated. Obtained results are compared with experimental values. Experimental data is used two-phase flow steam-water in VVER-1200, reactor coolant system, reactor operating pressure is 16.2 MPa. On heater rod surface, dryout was detected as a result of jumping increase of the heater rod surface temperature. Results obtained display lower droplet dimensions than the experimentally obtained values.

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