Electrocaloric cooling prototype using lead-free barium titanate multilayer capacitors and heat transfer fluid motion

2021 ◽  
pp. 1-17
Author(s):  
Said Bellafkih ◽  
Abdelhak Hadj-Sahraoui ◽  
Pierre Kulinski ◽  
Pierre Dumoulin ◽  
Stephane Longuemart
Keyword(s):  
Heat Transfer ◽  
Barium Titanate ◽  
Fluid Motion ◽  
Lead Free ◽  
Heat Transfer Fluid ◽  
Refrigeration Cycle ◽  
Electrocaloric Effect ◽  
Multilayer Capacitors ◽  
Oscillating Motion

Abstract In this paper, we describe the realisation and the testing of an electrocaloric effect based refrigeration prototype. The prototype makes use of Active Electrocaloric Regenerator (AER) made of commercially available MultiLayer ceramics and exploits the oscillating motion of a heat transfer fluid in a thermodynamic refrigeration cycle. The setup allows the adjustment of various parameters and the effect of the frequency of the cycle as well as the volume displaced of the heat transfer fluid has been evidenced. An amplification regenerative factor of 1.25 has been reached, comparable and slightly higher to those of previously proposed electrocaloric refrigerator prototypes.

Fluid Motion and Heat Transfer of a High-Viscosity Fluid in a Rectangular Tank on a Ship With Oscillating Motion

1987 ◽  
Vol 109 (3) ◽  
pp. 635-641 ◽  
Author(s):  
S. Akagi ◽  
K. Uchida
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Fluid Motion ◽  
Heating System ◽  
High Viscosity ◽  
Thermal Design ◽  
Basic Equations ◽  
Oil Tanks ◽  
Oscillating Motion ◽  
Viscosity Fluid

Fluid motion and heat transfer of a high-viscosity fluid contained in a two-dimensional rectangular ship’s tank subjected to oscillating motion are investigated by a finite difference technique. The study is motivated by the thermal design of the heating system of oil tanks on a tanker which is moving in a wavy sea. The bottom of the tank is heated and its side walls are cooled. The motion of the tank is assumed to be a simple harmonic rolling motion. The isotherms and flow velocity vectors are determined by numerical solutions of the basic equations describing the convection flows in a tank with oscillating motion. The heat transfer rates to the tank walls are predicted. The influence of the frequency of the oscillating motion on the heat transfer rate is examined.

Investigating the effect of using nanofluids on the performance of a double-effect absorption refrigeration cycle combined with a solar collector

2019 ◽  
Vol 234 (7) ◽  
pp. 981-993 ◽  
Author(s):  
Mohamad Aramesh ◽  
Fathollah Pourfayaz ◽  
Mehdi Haghir ◽  
Alibakhsh Kasaeian ◽  
Mohammad H Ahmadi
Keyword(s):  
Heat Transfer ◽  
Ag Nanoparticles ◽  
Pure Water ◽  
Double Effect ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Refrigeration Cycle ◽  
Outlet Temperature ◽  
Absorption Refrigeration

In this article, the performance of a double-effect LiBr-H2O absorption refrigeration cycle is studied and is improved by applying solar energy and utilizing nanofluids. A trough collector is used to preheat the working fluid before entering the generator of the cycle. In addition, four different nanofluids are considered as the heat transfer fluid of the collector: Al2O3, Ag, Cu, and CuO. The effects of using nanofluids on the outlet temperature of the heat transfer fluid, the temperature of the working fluid entering the generator, the heat produced by the generator, and COP of the cycle are studied. Different concentrations of the nanoparticles from 0 to 2.5% are considered for the nanofluids. The results indicate that in all the concentrations, Ag nanoparticles will have a better performance comparing to the other types. Furthermore, it was concluded that the higher concentrations of the nanoparticles and along with it the higher inlet temperature of the generator will decrease the generator heat production rate up to 4%. Moreover, considering the constant cooling capacity of the cycle, usage of the Ag nanoparticles in the concentration of 2.5% increases the value of COP up to 3.9%, with respect to the pure water.

Thermodynamic Analysis of Magnetic Refrigerators

2004 ◽  
Author(s):  
Muhammad M. Rahman ◽  
Luis Rosario
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Heat Exchangers ◽  
Room Temperature ◽  
Fluid Flows ◽  
Heat Transfer Fluid ◽  
Cooling Power ◽  
Refrigeration Cycle ◽  
Heating Effects ◽  
The Magnetic Field

An analysis of a magnetic refrigeration cycle was carried out. The system consists of heat exchangers and beds of magnetic materials. The analysis considered that the system operates near room temperature in a magnetic field between 1 and 5 T and uses 3 kg of gadolinium (Gd) spheres packed in two magnetocaloric beds. The heat transfer fluid is water. The beds are periodically magnetized and demagnetized and the fluid flows are arranged to meet the cycle requirements. Sensitivity analysis has been performed. Cooling power, magnetic field, and temperature span trends are simulated. The cooling and heating effects were estimated based on the magnetocaloric effect of gadolinium. Findings indicate that the higher the magnetic field is the higher the cooling power with the same temperature span. It was also observed that the cooling power decreases with the increase in the temperature span for various magnetic fields. COP vs. temperature span was also considered. The trend indicates that COPactual/ COPCarnot decreases with an increase in the temperature span. These trends agreed with those shown by experimental data.

INFLUENCE OF HEAT TREATMENT OF MOUNTAIN MASSIVE ON TEMPERATURE MODE OF GEOTHERMAL CIRCULATION SYSTEM

2018 ◽  
pp. 44-50
Author(s):  
Yu. P. Morozov
Keyword(s):  
Heat Transfer ◽  
Operating Time ◽  
Fluid Motion ◽  
Coolant Temperature ◽  
Circulation System ◽  
Thermal Processes ◽  
Temperature Mode ◽  
Heat Influx ◽  
Stationary Heat Transfer

Based on the solution of the problem of non-stationary heat transfer during fluid motion in underground permeable layers, dependence was obtained to determine the operating time of the geothermal circulation system in the regime of constant and falling temperatures. It has been established that for a thickness of the layer H <4 m, the influence of heat influxes at = 0.99 and = 0.5 is practically the same, but for a thickness of the layer H> 5 m, the influence of heat inflows depends significantly on temperature. At a thickness of the permeable formation H> 20 m, the heat transfer at = 0.99 has virtually no effect on the thermal processes in the permeable formation, but at = 0.5 the heat influx, depending on the speed of movement, can be from 50 to 90%. Only at H> 50 m, the effect of heat influx significantly decreases and amounts, depending on the filtration rate, from 50 to 10%. The thermal effect of the rock mass with its thickness of more than 10 m, the distance between the discharge circuit and operation, as well as the speed of the coolant have almost no effect on the determination of the operating time of the GCS in constant temperature mode. During operation of the GCS at a dimensionless coolant temperature = 0.5, the velocity of the coolant is significant. With an increase in the speed of the coolant in two times, the error changes by 1.5 times.

Experimental Study on Thermal Characteristics of Finned Coil LHSU Using Paraffin as Phase Change Material

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Guansheng Chen ◽  
Nanshuo Li ◽  
Huanhuan Xiang ◽  
Fan Li
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Phase Change ◽  
Phase Change Material ◽  
Water Flow ◽  
Water Flow Rate ◽  
Thermal Characteristics ◽  
Heat Transfer Fluid ◽  
Latent Heat Storage ◽  
Change Material

It is well known that attaching fins on the tubes surfaces can enhance the heat transfer into and out from the phase change materials (PCMs). This paper presents the results of an experimental study on the thermal characteristics of finned coil latent heat storage unit (LHSU) using paraffin as the phase change material (PCM). The paraffin LHSU is a rectangular cube consists of continuous horizontal multibended tubes attached vertical fins at the pitches of 2.5, 5.0, and 7.5 mm that creates the heat transfer surface. The shell side along with the space around the tubes and fins is filled with the material RT54 allocated to store energy of water, which flows inside the tubes as heat transfer fluid (HTF). The measurement is carried out under four different water flow rates: 1.01, 1.30, 1.50, and 1.70 L/min in the charging and discharging process, respectively. The temperature of paraffin and water, charging and discharging wattage, and heat transfer coefficient are plotted in relation to the working time and water flow rate.

scholarly journals Numerical Evaluation of a HVAC System Based on a High-Performance Heat Transfer Fluid

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3298
Author(s):  
Gianpiero Colangelo ◽  
Brenda Raho ◽  
Marco Milanese ◽  
Arturo de Risi
Keyword(s):  
Heat Transfer ◽  
High Performance ◽  
Cooling System ◽  
Electrical Energy ◽  
Simulation Software ◽  
Heat Transfer Fluid ◽  
Hvac System ◽  
Dynamic Simulations ◽  
Heating And Cooling ◽  
The University

Nanofluids have great potential to improve the heat transfer properties of liquids, as demonstrated by recent studies. This paper presents a novel idea of utilizing nanofluid. It analyzes the performance of a HVAC (Heating Ventilation Air Conditioning) system using a high-performance heat transfer fluid (water-glycol nanofluid with nanoparticles of Al2O3), in the university campus of Lecce, Italy. The work describes the dynamic model of the building and its heating and cooling system, realized through the simulation software TRNSYS 17. The use of heat transfer fluid inseminated by nanoparticles in a real HVAC system is an innovative application that is difficult to find in the scientific literature so far. This work focuses on comparing the efficiency of the system working with a traditional water-glycol mixture with the same system that uses Al2O3-nanofluid. The results obtained by means of the dynamic simulations have confirmed what theoretically assumed, indicating the working conditions of the HVAC system that lead to lower operating costs and higher COP and EER, guaranteeing the optimal conditions of thermo-hygrometric comfort inside the building. Finally, the results showed that the use of a nanofluid based on water-glycol mixture and alumina increases the efficiency about 10% and at the same time reduces the electrical energy consumption of the HVAC system.

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%.

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