scholarly journals Improving Heat Transfer from Peltier Devices Used in an Atmospheric Water Generation

2021 ◽  
Vol 6 (3) ◽  
pp. 170-175
Author(s):  
Mark Summers ◽  
Bahram Asiabanpour
Keyword(s):  
Heat Transfer ◽  
Convection Heat Transfer ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Conductive Heat ◽  
Vapor Compression ◽  
Solar Panels ◽  
Atmospheric Water ◽  
Thermoelectric Coolers ◽  
Phase Change Heat Transfer

Present Atmospheric Water Generation (AWG) systems are useful for providing water in areas with limited water supplies. Many industrial AWG systems use VCR (vapor-compression refrigeration) to achieve a large amount of cooling to extract liquid water out of the air.  These systems require large amounts of energy to operate, usually in the form of diesel or AC-powered generators.  The systems also have many moving parts that require maintenance and use refrigerants that can leak and cause problems with the environment. An alternative AWG solution is to use DC-powered Peltier devices (thermoelectric coolers) to reduce the temperature of condensation plates to extract water from the air.  This solution eliminates the issues with traditional industrial AWG systems since the Peltier devices are solid-state, have very long mean-time between failure (MTBF) performance, and can be powered by solar panels that eliminate the need to burn hydrocarbon-based fuels or have access to a reliable power grid.  Also eliminated is the need to use chlorofluorocarbon (CFC) or hydrochlorofluorocarbons (HCFC) refrigerants that have been shown to deplete the ozone layer. This paper will present methods to improve the efficiency of the thermoelectric coolers by more efficiently extracting heat from the hot side of the device.  This efficiency will be quantified by evaluating the coefficient of performance (COP) of the thermoelectric cooler under the various operating conditions.  Different combinations of conductive heat transfer using aluminium heatsinks, convection heat transfer using forced airflow, and phase change heat transfer using copper heat pipes filled with distilled water will be investigated and evaluated.

An Experimental Investigation on Vapor Compression Refrigeration System Cascaded with Ejector Refrigeration System

2021 ◽  
pp. 2150028
Author(s):  
Vikas Kumar ◽  
Gulshan Sachdeva ◽  
Sandeep Tiwari ◽  
Parinam Anuradha ◽  
Vaibhav Jain
Keyword(s):  
Experimental Investigation ◽  
Thermal Equilibrium ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Compression System ◽  
Vapor Compression System ◽  
Vapor Compression Refrigeration ◽  
Cascaded System

A conventional vapor compression refrigeration system (VCRS) cascaded with a heat-assisted ejector refrigeration system (ERS) has been experimentally analyzed. Cascading allows the VCRS to operate at lower condenser temperatures and thus achieve a higher coefficient of performance. In this cascaded system, the condenser of the vapor compression system does not dissipate its heat directly to the evaporator of the ERS; instead, water circulates between the condenser of VCRS and the evaporator of ERS to exchange the heat. Seven ejectors of different geometries have been used in the ERS; however, all the ejectors could not maintain thermal equilibrium at the desired operating conditions. The compressor of the cascaded VCRS consumed 1.3 times less power than the noncascaded VCRS. Furthermore, the cascaded system provided a maximum 87.74% improvement in COP over the noncascaded system for the same operating conditions. The performance of the system remained constant until the critical condenser pressure of the ERS.

scholarly journals Parametric analysis of a combined ejector-vapor compression refrigeration cycle

2020 ◽  
Vol 15 (3) ◽  
pp. 398-408
Author(s):  
I Ouelhazi ◽  
Y Ezzaalouni ◽  
L Kairouani
Keyword(s):  
Current Model ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Refrigeration System ◽  
Entrainment Ratio ◽  
Constant Area ◽  
Vapor Compression Refrigeration Cycle ◽  
Vapor Compression Refrigeration

Abstract From the last few years, the use of efficient ejector in refrigeration systems has been paid a lot of attention. In this article a description of a refrigeration system that combines a basic vapor compression refrigeration cycle with an ejector cooling cycle is presented. A one-dimensional mathematical model is developed using the flow governing thermodynamic equations based on a constant area ejector flow model. The model includes effects of friction at the constant-area mixing chamber. The current model is based on the NIST-REFPROP database for refrigerant property calculations. The model has basically been used to determine the effect of the ejector geometry and operating conditions on the performance of the whole refrigeration system. The results show that the proposed model predicts ejector performance, entrainment ratio and the coefficient of performance of the system and their sensitivity to evaporating and generating temperature of the cascade refrigeration cycle. The simulated performance has been then compared with the available experimental data from the literature for validation.

Thermoelectric Heat Pipe-Based Refrigerator: System Development and Comparison with Thermoelectric, Absorption and Vapor Compression Refrigerators

2013 ◽  
Vol 651 ◽  
pp. 736-744
Author(s):  
Nandy Putra ◽  
H. Ardiyansya ◽  
Ridho Irwansyah ◽  
Wayan Nata Septiadi ◽  
A. Adiwinata ◽  
...  
Keyword(s):  
Heat Pipe ◽  
Heat Dissipation ◽  
System Development ◽  
Coefficient Of Performance ◽  
Prototype System ◽  
Vapor Compression ◽  
Thermoelectric Coolers ◽  
Thermoelectric Systems ◽  
Vapor Compression System ◽  
Thermoelectric Heat

Thermoelectric coolers have been widely applied to provide cooling for refrigerators in addition to conventional absorption and vapor compression systems. To increase heat dissipation in the thermoelectric cooler’s modules, a heat pipe can be installed in the system. The aim of this study is to develop a thermoelectric heat pipe-based (THP) refrigerator, which consists of thermoelectric coolers that are connected by heat pipe modules to enhance heat transfer. A comparative analysis of the THP prototype and conventional refrigerator with vapor compression, absorption and thermoelectric systems is also presented. The prototype system has a faster cooling down time and a higher coefficient of performance than the absorption system but still lower than vapor compression system

Analytical and Experimental Study of Combustion and Heat Transfer in Submerged Flame Metal Fiber Burners/Heaters

2003 ◽  
Vol 125 (1) ◽  
pp. 118-125 ◽  
Author(s):  
S. A. Leonardi ◽  
R. Viskanta ◽  
J. P. Gore
Keyword(s):  
Heat Transfer ◽  
Solid Phase ◽  
Convection Heat Transfer ◽  
Single Layer ◽  
Operating Conditions ◽  
Solid Matrix ◽  
Discrete Ordinates ◽  
Metal Fiber ◽  
Burner Surface ◽  
Exhaust Temperature

A theoretical model has been developed to predict the thermal performance of inert, direct-fired, woven-metal fiber-matrix porous radiant burner. The local chemical heat release was modeled by a detailed mechanism, and convection heat transfer between the gas and the solid phases in the burner was described by an empirical heat transfer coefficient. The solid matrix was modeled as a gray medium, and the discrete ordinates method was used to solve the radiative transfer equation to calculate the local radiation source/sink in the energy equation for the solid phase. The fully coupled nature of the calculations without external specification of flame location represents a key advance over past efforts towards modeling of porous radiant burners, because for a given mass flow rate the actual heat loss from the flame determines its position and is not a free parameter. The calculated results for the burner surface temperature, the gas exhaust temperature and the radiation efficiency for a single layer Fecralloy burner were compared with experimental data from this laboratory and reasonable agreement was obtained for a range of operating conditions.

Transient Forced Convection Heat Transfer to Helium During a Step in Heat Flux

1983 ◽  
Vol 105 (2) ◽  
pp. 350-357 ◽  
Author(s):  
P. J. Giarratano ◽  
W. G. Steward
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Forced Convection ◽  
Carbon Film ◽  
Convection Heat Transfer ◽  
Fast Response ◽  
Operating Conditions ◽  
Convection Heat ◽  
Transfer Coefficients ◽  
Forced Convection Heat Transfer

Transient forced convection heat transfer coefficients for both subcritical and supercritical helium in a rectangular flow channel heated on one side were measured during the application of a step in heat flux. Zero flow data were also obtained. The heater surface which served simultaneously as a thermometer was a fast response carbon film. Operating conditions covered the following range: Pressure, 1.0 × 105 Pa (1 bar) to 1.0 × 106 Pa (10 bar); Temperature, 4 K–10 K; Heat Flux, 0.1 W/cm2−10 W/cm2; Reynolds number, 0–8 × 105. The experimental data and a predictive correlation are presented.

An Experimental Study of Combustor Exit Profile Shapes on Endwall Heat Transfer in High Pressure Turbine Vanes

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
M. D. Barringer ◽  
K. A. Thole ◽  
M. D. Polanka
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Elevated Temperatures ◽  
Convection Heat Transfer ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
High Pressure Turbine ◽  
Radial Profiles ◽  
Temperature And Pressure

The design and development of current and future gas turbine engines for aircraft propulsion have focused on operating the high pressure turbine at increasingly elevated temperatures and pressures. The drive toward thermal operating conditions near theoretical stoichiometric limits as well as increasingly stringent requirements on reducing harmful emissions both equate to the temperature profiles exiting combustors and entering turbines becoming less peaked than in the past. This drive has placed emphasis on determining how different types of inlet temperature and pressure profiles affect the first stage airfoil endwalls. The goal of the current study was to investigate how different radial profiles of temperature and pressure affect the heat transfer along the vane endwall in a high pressure turbine. Testing was performed in the Turbine Research Facility located at the Air Force Research Laboratory using an inlet profile generator. Results indicate that the convection heat transfer coefficients are influenced by both the inlet pressure profile shape and the location along the endwall. The heat transfer driving temperature for inlet profiles that are nonuniform in temperature is also discussed.

A CFD Assessment of Engine Core Zone Casing Heat Transfer

2019 ◽  
Author(s):  
Zixiang Sun ◽  
Nicholas J. Hills ◽  
Richard Scott
Keyword(s):  
Heat Transfer ◽  
Radiation Heat Transfer ◽  
Convection Heat Transfer ◽  
Aircraft Engine ◽  
Operating Conditions ◽  
Steady Flows ◽  
Radiation Heat ◽  
Core Zone ◽  
The Public ◽  
The Core

Abstract A systematic CFD investigation was conducted to assess the core zone (CZ) casing heat transfer of a large civil aircraft engine. Three key engine operating conditions, maximum takeoff (MTO), cruise (CRZ) and ground idle (GI) were analyzed. Steady flows were assumed. Turbulence was simulated using the realizable k-epsilon model in conjunction with the scalable wall function. Buoyancy effect was taken into account. Radiation was calculated using the discrete ordinate (DO) model. It was shown that the forced convection heat transfer dominates in most of the casing surface in the core zone, and radiation is of second importance in general. However, in some areas where both convection and radiation heat transfer are weak but the latter is relatively greater in magnitude than the former, radiation heat transfer could thus become dominant. In addition, the overall impact of radiation on casing heat transfer increases from MTO to CRZ and GI conditions, as the strength of engine load decreases. The overall effect of buoyancy on casing heat transfer is small, but could be noticeable in some local areas where flow velocity is low. The insight into heat transfer features on the engine core zone casing supported by quantified CFD evidences is the first in the public domain, as far as authors are aware.

Understanding the Heat-Transfer Mechanism in the Steam-Assisted Gravity-Drainage (SAGD) Process and Comparing the Conduction and Convection Flux in Bitumen Reservoirs

SPE Journal ◽  
2013 ◽  
Vol 18 (01) ◽  
pp. 179-188 ◽  
Author(s):  
Mazda Irani ◽  
Sahar Ghannadi
Keyword(s):  
Heat Transfer ◽  
Water Saturation ◽  
Convection Heat Transfer ◽  
High Water ◽  
Thermal Recovery ◽  
Transfer Mechanism ◽  
Injection Well ◽  
Conductive Heat ◽  
Heat Transfer Mechanism ◽  
Peace River

Summary SAGD is one successful thermal recovery technique applied in the Athabasca and Peace River reservoirs in central and northern Alberta, Canada. In SAGD, steam is injected into a horizontal injection well and is forced outward, losing its latent heat when it comes into contact with the cold bitumen at the edge of a depletion chamber. As a consequence, the viscosity of the bitumen falls several orders of magnitude, its mobility rises several orders of magnitude, and then it flows under gravity toward a horizontal production well located several meters below and parallel to the injection well. Heat-transfer mechanisms are pivotal to the SAGD process. Though heat energy is transferred from steam to reservoir by conduction and convection, heat transfer by convection is not considered in the classic SAGD mathematical models such as Butler's. Researchers such as Butler and Stephens (1981), Reis (1992), Akin (2005), Liang (2005), Nukhaev et al. (2006), and Azad and Chalaturnyk (2010) considered conduction from steam to cold reservoir to be the only heat-transfer component. However, because the heat capacity of water is typically two to five times that of bitumen, convection caused by the mobile condensate flow in the reservoir may contradict these studies. Farouq-Ali (1997) was the first to criticize the assumption that there is only a thermal conduction mechanism in the SAGD process. He pointed out that with so much condensate flowing, convection would be expected to be the dominant heat-transfer mechanism, which can be plausible at high temperatures. In response, Edmunds (1999a) stated that on the basis of the associated change in enthalpy, the heat transfer into a cold reservoir because of convection is probably less than 5% of that because of conduction. Ito (1999) challenged Edmunds (1999a) statement, on the basis of Ito and Suzuki (1996, 1999) and Ito et al. (1998), pointing out that “this number, 5%; i.e., ratio between convection to conduction presented by Edmunds (1999a) is unrealistically low, (and) it should be in the range of 50%.” This study examined the relative roles of convective and conductive heat transfer at the edge of SAGD steam chambers. In summary, the mathematical model developed in this study considered both conduction and convection, and the resultant output from the model is reasonably consistent with published field data. This study supports the idea that although convection can dominate near the chamber edge in high-water-saturation reservoirs, in bitumen-rich reservoirs, its contribution to heat transfer is less than 1% and can be neglected.

Understanding the Heat-Transfer Mechanism in the Steam-Assisted Gravity-Drainage (SAGD) Process and Comparing the Conduction and Convection Flux in Bitumen Reservoirs

SPE Journal ◽  
2013 ◽  
Vol 18 (01) ◽  
pp. 134-145 ◽  
Author(s):  
Mazda Irani ◽  
Sahar Ghannadi
Keyword(s):  
Heat Transfer ◽  
Water Saturation ◽  
Convection Heat Transfer ◽  
High Water ◽  
Thermal Recovery ◽  
Transfer Mechanism ◽  
Injection Well ◽  
Conductive Heat ◽  
Heat Transfer Mechanism ◽  
Peace River

Summary SAGD is one successful thermal recovery technique applied in the Athabasca and Peace River reservoirs in central and northern Alberta, Canada. In SAGD, steam is injected into a horizontal injection well and is forced outward, losing its latent heat when it comes into contact with the cold bitumen at the edge of a depletion chamber. As a consequence, the viscosity of the bitumen falls several orders of magnitude, its mobility rises several orders of magnitude, and then it flows under gravity toward a horizontal production well located several meters below and parallel to the injection well. Heat-transfer mechanisms are pivotal to the SAGD process. Though heat energy is transferred from steam to reservoir by conduction and convection, heat transfer by convection is not considered in the classic SAGD mathematical models such as Butler?s. Researchers such as Butler and Stephens (1981), Reis (1992), Akin (2005), Liang (2005), Nukhaev et al. (2006), and Azad and Chalaturnyk (2010) considered conduction from steam to cold reservoir to be the only heat-transfer component. However, because the heat capacity of water is typically two to five times that of bitumen, convection caused by the mobile condensate flow in the reservoir may contradict these studies. Farouq-Ali (1997) was the first to criticize the assumption that there is only a thermal conduction mechanism in the SAGD process. He pointed out that with so much condensate flowing, convection would be expected to be the dominant heat-transfer mechanism, which can be plausible at high temperatures. In response, Edmunds (1999a) stated that on the basis of the associated change in enthalpy, the heat transfer into a cold reservoir because of convection is probably less than 5% of that because of conduction. Ito (1999) challenged Edmunds (1999a) statement, on the basis of Ito and Suzuki (1996, 1999) and Ito et al. (1998), pointing out that "this number, 5%; i.e., ratio between convection to conduction presented by Edmunds (1999a) is unrealistically low, (and) it should be in the range of 50%. This study examined the relative roles of convective and conductive heat transfer at the edge of SAGD steam chambers. In summary, the mathematical model developed in this study considered both conduction and convection, and the resultant output from the model is reasonably consistent with published field data. This study supports the idea that although convection can dominate near the chamber edge in high-water-saturation reservoirs, in bitumen-rich reservoirs, its contribution to heat transfer is less than 1% and can be neglected.

scholarly journals Гибридные режимы работы термоэлектрических модулей

2022 ◽  
Vol 56 (1) ◽  
pp. 13
Author(s):  
И.А. Драбкин ◽  
Л.Б. Ершова
Keyword(s):  
Cooling Capacity ◽  
Operating Conditions ◽  
Coefficient Of Performance ◽  
Large Temperature ◽  
Hybrid Mode ◽  
Cooling Mode ◽  
Thermoelectric Coolers ◽  
General Cooling ◽  
Maximum Coefficient

It is suggested that thermoelectric coolers designing should not be limited to the extreme modes of their operation. In some cases, it is convenient to use the so called hybrid modes - a combination of the extreme mode of maximum coefficient of performance for large temperature differences and a general cooling mode for small ones. The proposed hybrid mode makes it possible to control the cooling capacity of the module and not to confine this value to that under the extreme operating conditions, the maximum coefficient of performance in particular.

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