Refrigeration Devices Research Articles

Thermal Management: Electrostatic Actuating Double‐Unit Electrocaloric Cooling Device with High Efficiency (Adv. Energy Mater. 13/2021)

In article number 2003771, Rujun Ma and co-workers report a highly efficient double-unit solid-state refrigeration device based on two-layer modified electrocaloric polymer stacks actuated by electrostatic forces. The availability and the high-efficiency of the device for cooling the central processing unit provides a unique option for thermal management of microcircuits in the future.

Concept design and numerical evaluation of a highly efficient rotary electrocaloric refrigeration device

Abstract Enabled by the discovery of giant electrocaloric effect (ECE) in inorganic ceramics and organic polymers, Electrocaloric (EC) cooling technology has attracted considerable attention from both academia and industrial. However, there remains many challenges in the refrigeration efficiency and/or capacity of the currently reported electrocaloric refrigeration devices. In this work, we propose a concept design of EC refrigeration device, in which the working bodies are rotating in a plane perpendicular to the direction of fluid flow. The rotary EC device adopting heat transfer fluid as an intermediate medium allows for improved heat exchange between EC materials and outside environment, and efficiently delivers cooling effects to where it’s needed. Simulations have been performed to investigate the system cooling performance under different operating strategies. Meanwhile, comparative researches on different heat transfer fluid are conducted and the corresponding cooling effects are studied. When using deionized water as heat transfer medium, the system can achieve a cooling power density of 9.89 W·cm−3 and COP of 10.48 over 10 K temperature span. In general, this work provides a highly-efficient rotary EC refrigeration device concept that employs fluid–solid conjugated heat transfer, and guides the optimization of operating strategy and selection of heat transfer fluid.

An empirical model for predicting the length of a capillary tube

AbstractAny refrigerant device consists of several parts, and one of the most significant parts is the expansion device. This expansion device can be classified into several types according to the size of the refrigeration system. The capillary tube is used usually with a small refrigerant system size to reduce the higher pressure in the condenser into the low pressure in the evaporator. In this study, the effect of the capillary tube's diameter and that of the temperature of the condenser and evaporator on the length of such a device has been theoretically studied. Furthermore, a validation between the theoretical analysis and experimental findings from the literature review has been carried out. To achieve the theoretical aspect, MATLAB code has been developed. The results showed that the maximum difference between the theoretical and experimental results regarding temperature and pressure refrigeration is around 5% and 3.4%, respectively. Also, the results depict that the inner diameter and the condenser temperature have an effect on the length of the capillary tube. However, the effect of the inner diameter is higher compared with the condenser temperature. In addition, an equation to predict the length of the capillary tube has been developed with an accuracy of 98%. This equation is created as a function of the capillary tube's diameter and the temperature of the condenser and the evaporator. Moreover, this equation can be used to predict the length of the capillary tube for small refrigeration devices, especially those operating under 10 KW. The findings of this study can help make a mathematical approach used for the design of the capillary tube simpler and easier to apply.

Electrostatic Actuating Double‐Unit Electrocaloric Cooling Device with High Efficiency

AbstractCompact solid‐state refrigeration systems that offer a high specific cooling power and a high coefficient of performance (COP) are desirable in a wide range of applications where efficient and localized heat transfer is required. Here, a double‐unit electrocaloric (EC) polymer‐based refrigeration device with high intrinsic thermodynamic efficiency is demonstrated using a flexible EC polymer film with improved performance by doping plasticizer and an electrostatic actuation mechanism. The double‐unit refrigeration device achieves a large temperature span of 4.8 K, which is 71% higher than that of the single‐unit device. A specific cooling power of 3.6 W g−1 and a maximum COP of 8.3 for the cooling device are produced. The surface temperature of a central processing unit (CPU) cooled by an active EC device is 22.4 K lower than that of the CPU cooled in air. The highly efficient and compact EC cooling device demonstrated here not only leapfrogs the performance of existing solid‐state cooling technologies, but also brings solid state cooling closer to reality for a variety of practical applications that require compact or mechanically flexible refrigeration.

Electric field induced phase transitions and electrocaloric effect of La3+ doped Pb(Zr,Sn,Ti)O3 ceramics

Electrocaloric effect (ECE) is considered well applicable in the field of next generation solid state refrigeration technology. In this article, the structural properties and ECE response were altered and optimized by tailoring the Zr/Ti molar ratio in (Pb0.94La0.04)(ZrxSn0.30Ti0.70-x)O3 (x = 0.54, 0.52, 0.50 and 0.48) polycrystalline ceramics. Multiple phase transition behaviors including antiferroelectric (AFE) state to ferroelectric (FE) state transition under applied electric field, depolarization phase change behavior and AFE state to paraelectric state (PE) transition were observed, and their effects on the ECE response were investigated in detail. Significant improvement of ECE adiabatic temperature change of 1.04 K at room temperature (30 °C) was obtained by Maxwell method in (Pb0.94La0.04)(Zr0.52Sn0.30Ti0.18)O3 bulk ceramic through AFE→FE phase transition, while the highest ΔT of 2.73 K with electrocaloric strength (ΔT·ΔE−1) of 0.039 K cm kV−1 were observed in (Pb0.94La0.04)(Zr0.50Sn0.30Ti0.20)O3 bulk ceramic at temperature close to its Curie peak. The high ECE temperature change and ECE strength make them to be candidates for using in next generation solid-state refrigeration device.

Effects of transitional hysteresis on the large magnetocaloric and magnetoresistance properties of Ni-Mn-Co-Sn Heusler alloy

Ni-Mn-Co-Sn based Heusler alloys have drawn immense attention lately due to their significant magnetocaloric (MC) and magnetoresistance (MR) properties near their first-order magneto-structural martensite transformation (MT). Here, we have studied the influence of thermal and magnetic hysteretic behaviours in the temperature and field dependent magnetization and resistivity in Ni45Mn39Co5Sn11 bulk Heusler alloy across the MT regime. This is critical since hysteresis losses could significantly compromise the MC and MR properties in these compounds in practical applications. Isothermal X-ray diffraction measurements at different temperatures reveal that the MT temperature is near room temperature in Ni45Mn39Co5Sn11 alloy. Thermodynamic analyses of isothermal field dependent magnetization data result in large isothermal magnetic entropy changes (ΔS = 17–18 J kg−1 K−1) under a field change (ΔH = 8 T) at 364 K across the MT regime. The calculated refrigeration capacity values (RC = 173–179 J kg−1) for decreasing and increasing fields are significant and independent of magnetic hysteresis across the MT regime. A large adiabatic temperature change (│ΔT│ = 10.4 K for ΔH = 8 T at 364 K) is being reported in Ni45Mn39Co5Sn11 Heusler alloy, which makes it promising for MC applications. Further, the influence of martensite-austenite phase fractions on the MC and MR properties in Ni45Mn39Co5Sn11 alloy has been studied across the MT regime using isofield and isothermal magnetic and magneto-transport measurements. A strong correlation has been established between the observed MR (−36.8%) and the transformed austenite phase fraction using both experimental data and theoretical model. The large RC, │ΔT│, MR values close to the room temperature and the role played by the thermal and magnetic hystereses on the MC and MR properties make the Ni45Mn39Co5Sn11 Heusler alloy an interesting material for technological applications in magnetic refrigeration and switching devices.

Front-end Solar Temperature And Humidity Control System

Solid dehumidification is one of the important components of the dehumidification air-conditioning system. As an important method of solid dehumidification, the dehumidification performance and regeneration performance of fixed-bed dehumidification have an important impact on the operation and energy saving of the dehumidification air-conditioning system. In view of the high air temperature and high humidity in South China, our design organically combines dehumidification fixed beds, semiconductor refrigeration devices, foam ceramic insulation panels and double-glazed windows. We have designed a photovoltaic-driven modular solar temperature regulating and dehumidifying purification wall suitable for building dehumidification. The dehumidification window can use daytime solar radiation to regenerate the dehumidification fixed bed after absorbing moisture, reducing the energy consumption of regeneration. At the same time, the design can also use semiconductor refrigeration devices to adjust the temperature and humidity of the window inlet air to improve the window's dehumidification and regeneration performance. We tested and studied the dehumidification and regeneration performance of the device under different working conditions through experimental tests, which provided a basis for the engineering application and theoretical analysis of the device.

Dilution refrigerator and its heat transfer problems

In the research of cryogenic physics and quantum information science, it is essential to maintain a steady low temperature of millikelvin regime continuously. Dilution refrigerator is a widely used refrigeration device to achieve extremely low temperature. It utilizes the phase separation effect of superfluid <sup>4</sup>He and its isotope <sup>3</sup>He mixed solution at ultra-low temperatures. The performance of heat exchanger is the key factor to determine the performance of continuous cycle refrigerating machine. At extremely low temperatures, there appears a huge interfacial thermal resistance between helium and metal (Kapitza resistance), and the problem of heat exchange can be effectively solved by using the porous sintered metal particles to increase the contact area. Therefore, it is of significance to study the heat exchange between metal particles and liquid helium at extremely low temperature and to develop the relevant high-performance sintered Ag powder heat exchanger.

A METHOD OF PREDICTING THE WATER TEMPERATURE APPLICABLE TO A SEMICONDUCTOR REFRIGERATION DEVICE

A METHOD OF PREDICTING THE WATER TEMPERATURE APPLICABLE TO A SEMICONDUCTOR REFRIGERATION DEVICE

Large Energy Storage Density and Electrocaloric Strength of Pb <sub>0.97</sub>La <sub>0.02</sub>(Zr <sub>0.46-x</sub>Sn <sub>0.54</sub>Ti <sub>x</sub>)O <sub>3</sub> Antiferroelectric Thick Film Ceramics

Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 (PLZST, x=0.04, 0.06, 0.08, 0.15, and 0.18) antiferroelectric thick film ceramics were fabricated via a tape-casting approach. The energy storage performance and electrocaloric effect were investigated in terms of the measurements on the hysteresis loops and Maxwell relation. The maximum value of energy storage density of 5.2 J/cm3 and efficiency of 78.2 % were procured at 600 kV/cm in Pb0.97La0.02(Zr0.42-xSn0.54Ti0.04)O3 thick film ceramics at room temperature. In addition, the ECE was indirectly calculated using the Maxwell relation and the P-E loops as a function of temperature and electric field, a reversible adiabatic temperature change of ΔT=2.47 °C was presented in Pb0.97La0.02(Zr0.42-xSn0.54Ti0.04)O3 thick film ceramics at 500 kV/cm, corresponding to the calculated electrocaloric strength of 0.48 K(MV/m)-1. These results indicate that the PLZST thick film ceramics are promising for practical applications in high-power energy storage capacitors and solid-state refrigeration devices.

Multicaloric effects in metamagnetic Heusler Ni-Mn-In under uniaxial stress and magnetic field

The world's growing hunger for artificial cold, on the one hand, and the ever more stringent climate targets, on the other, pose an enormous challenge to mankind. Novel, efficient, and environmentally friendly refrigeration technologies based on solid-state refrigerants can offer a way out of the problems arising from climate-damaging substances used in conventional vapor-compressors. Multicaloric materials stand out because of their large temperature changes, which can be induced by the application of different external stimuli such as a magnetic, electric, or a mechanical field. Despite the high potential for applications and the interesting physics of this group of materials, few studies focus on their investigation by direct methods. In this paper, we report on the advanced characterization of all relevant physical quantities that determine the multicaloric effect of a Ni-Mn-In Heusler compound. We have used a purpose-designed calorimeter to determine the isothermal entropy and adiabatic temperature changes resulting from the combined action of magnetic field and uniaxial stress on this metamagnetic shape-memory alloy. From these results, we can conclude that the multicaloric response of this alloy by appropriate changes of uniaxial stress and magnetic field largely outperforms the caloric response of the alloy when subjected to only a single stimulus. We anticipate that our findings can be applied to other multicaloric materials, thus inspiring the development of refrigeration devices based on the multicaloric effect.

Soft Perovskite-Type Antiferroelectric with Giant Electrocaloric Strength near Room Temperature.

Antiferroelectric materials, characterized by an antiparallel array of adjacent dipoles, are holding a bright future for solid-state refrigeration based on their electrocaloric (EC) effects. Despite great advances of inorganic oxides and some organic soft polymers, their EC effects are achieved under quite high electric fields that result in too low EC strengths for practical application. Currently, it is a challenge to exploit soft antiferroelectric with strong EC strengths. Here, by the mixed-cation alloying, we present a new perovskite-type soft antiferroelectric, (isopentylammonium)2CsPb2Br7 (1), which incorporates both an organic spacing cation and an inorganic perovskitizer Cs+ moiety. Remarkably, the synergic cooperativity between the reorientation of the organic spacer and atomic displacement of Cs+ cation triggers its multiple ferroelectric-antiferroelectric-paraelectric phase transitions at 321 and 350 K. Their natural polarization vs electric field hysteresis loops are characterized to confirm ferroelectric and antiferroelectric orders of 1, respectively. It is emphasized that, under a low electric field of 13 kV/cm, the antipolar dipole realignment in 1 endows a giant near-room-temperature EC strength (ΔTEC/ΔE) of 15.4 K m MV-1 at antiferroelectric phase. This merit is on par with the record-high value of BaTiO3 (∼16 K m/MV) but far beyond the state-of-the-art soft polymers. The underlying EC mechanism for 1 is ascribed to the extremely low critical field to switch dipoles, involving the reorientation of the organic spacer and the shift of the Cs+ cation. Besides, notable EC entropy change (∼4.1 J K-1 kg-1) and temperature change (∼2 K) reveal potentials of 1 for solid-state refrigeration. As far as we know, this discovery of near-room-temperature EC strengths is unprecedented in the hybrid perovskite family, which sheds light on the exploration of new soft antiferroelectrics toward high-efficiency refrigeration devices.

Enhanced electrocaloric effect in compositional driven potassium sodium niobate-based relaxor ferroelectrics

Abstract

Design and Simulation of Multi-nozzle FDM 3D printer for fabricated Solar thin-film cells

In order to widely realize the personalized use of solar thin-film cells in every family, save costs and generate clean energy, our team wants to fabricate a 3D printer of solar thin-film cells. The solar film cells were 3D printed fabrication by FDM3D printer would improve their performance as battery. In this paper, for fabricate P nano-diamond/ZnO solar film cells the hot bed and nozzle of 3D printer were designed to achieve 3D printing of solar cells. A printer for fabricated solar thin-film cells was designed. PID was used to set the temperature of printer nozzle, and a refrigeration device was added to the substrate. And then finally, the printing device was simulated by SW.

Elastocaloric effect in bamboo-grained Cu71.1Al17.2Mn11.7 microwires

Bamboo-grained Cu71.1Al17.2Mn11.7 microwires with diameter ∼150 μm were created by Taylor-Ulitovsky method and subsequent annealing. The grain architecture dependent superelasticity (SE) and elastocaloric effects (eCE) were confirmed. The bamboo-grained microwires exhibited low stress hysteresis loss during SE due to the reduced constraints caused by grain boundary, which is favorable for the mobility of martensite-austenite interface. Consequently, a large isothermal entropy change ∼21 J/kg K with a wide temperature range 90 K was achieved. The produced adiabatic temperature change (ΔTad) reached −11.9 K under a maximum stress 400 MPa. A stable ΔTad of −5.6 K showing little degradation in 200 eCE cycles was found with applied stress 325 MPa. This work reveals a fact that the bamboo-grained Cu–Al–Mn microwire may act as a desirable material for miniature solid-state refrigeration devices.

A successful process to prevent corrosion of rich Gd-based room temperature magnetocaloric material during ageing

When the heat transport processes occur in a magnetic refrigeration device, there is possibility of corrosion thereforth, insight on the magnetocaloric regenerator corrosion could be shed in light. Our work mimicks this phenomenon by subjecting the magnetocaloric material Gd6Co1.67Si3 to controlled water flow. The corrosion is first explained based on the elemental electrochemical oxidation thereby allowing a new test by the exposing material in passive fluid (KOH) up to 1 year. The neglected degradation of the material was justified by X-Ray photoelectron spectroscopy (XPS) and depth profile Auger spectroscopy, and thus the control of its corrosion is reported. The effective control of the corrosion when material is exposed to KOH could be a universal procedure in magnetic refrigeration prototype.

Effect of Smart Glazing Window on Energy Consumption inside Office Building

The office buildings in Egypt, especially in Upper Egypt, reflect serious problems in achieving for energy efficiency as a result of increasing the use of mechanical refrigeration devices in office rooms, due to solar radiation and rising summer temperatures in recent years. Smart windows can play an important role in reducing significantly the energy consumption and maintaining energy inside buildings, also helps to control incoming solar radiation in order to minimize solar gain, especially in summer as well as ensuring the best natural lighting conditions without glare inside a room. This paper aims to evaluate the most efficient daylight and thermal performance of various types of the smart glazing and its impact on the energy consumption in the climatic conditions of one of the office buildings (Diwan governorate) in Sohag governorate as one of Upper Egypt governorates, with determining the best smart glass types for efficient use of energy. The paper follows the theoretical, applied, by studying types of smart glazing and their relation to achieving the energy efficiency. Then using (Energy Plus) simulation tool, which has been used in utilizing its modeling orientation (Design Builder) to study using types of smart glazing on the model of an office room in Building of Diwan governorate of Sohag in the four different orientations (North, East, South and West), when window-to-floor ratios (WFRs) (8%, 16%, 24% and 32%). The paper ends with a presentation of the most important results, recommendations and determination the best types of smart glass that provides energy, daylight without glare and providing greater comfort to users.

IMPROVEMENT OF OPERATION MODES OF THE EVAPORATOR OF THE ABSORPTION REFRIGERATING UNIT

Absorption refrigeration units (ARU), which are part of absorption refrigeration devices (ARD) with a natural working fluid (water, ammonia and hydrogen) have a number of unique qualities. These qualities include: noiselessness, high reliability and long life; the possibility of using several energy sources in one device. At the same time, ARDs have increased energy consumption compared to similar compression models, and this does not allow them to expand their presence in the market of household refrigeration equipment. The ARU evaporator provides a predetermined temperature level in the chambers of the refrigeration appliance and the required cooling capacity. In this regard, it is relevant to search for the operating modes of the evaporator that provide the ARU maximum energy efficiency, which is the aim of this work. The thermal conditions of the direct-flow three-pipe design of the evaporator are simulated. The calculated ratio for a once-through evaporator is obtained taking into account the assumption of the adiabaticity of the evaporation process, when all the heat of the phase transition is used to cool the incoming flows of the purified vapor-gas mixture (VGM) and liquid ammonia to a minimum temperature. The analysis of the results of calculating the operating modes of the evaporator made it possible to determine the directions of ways to increase the energy efficiency of both the evaporator itself and the ARU in general: a) preliminary cooling of the purified VGM flow at the inlet of the adiabatic section of the evaporator with an under-recovery of up to 5 °C and up to 10 °C; b) preliminary cooling of the liquid ammonia flow at the inlet of the adiabatic section of the evaporator with an under-recovery of up to 5 °C for all ARU types; c) increasing the purification degree of the VGM flow in the absorber allows increasing the temperature of the purified VGM flow at the inlet of the adiabatic section of the evaporator by 4...6 °C, i. e. to reduce the costs of useful cooling capacity for pre-cooling by 10...15 %

Design and optimisation of an advanced waste heat cascade utilisation system for a large marine diesel engine

Growing energy shortages severely restricting the sustainable development of human beings, improving energy efficiency has become an urgent issue. To improve energy efficiency, the dual-pressure organic Rankine cycle, which is an efficient waste heat recovery technique for ships, has received increasing attention. Most researchers have investigated the dual-pressure organic Rankine cycle with pure working fluids, which do not yield the best thermodynamic and economic performance. In addition, some low-grade waste heat sources in the engine have been neglected. To completely recover the waste heat energy of marine engines, a novel waste heat recovery technique with a dual-pressure organic Rankine cycle system, desalination plant, and two-bed regenerative adsorption refrigeration device is presented for recovering residual heat from the exhaust gas, jacket water, charge air, and lubricating oil. Based on a comparison of the thermodynamic performance, safety, and environmental effects, the zeotropic working fluid pair dimethyl carbonate/perfluoropropane is selected. The mathematical model of the proposed integrated system is evaluated to ensure accuracy, and its critical parameters are analysed based on its thermodynamic and economic performance. A multi-objective artificial bee colony algorithm is adopted to optimise the system. The results show that the proposed integrated system can recover 354.65 kW net power and increase the thermal efficiency by 4.2% on average; at the most frequently used engine load, a refrigeration capacity of 88 kW and a fresh water rate of 146 kg/h are achieved. This work promotes the development of the energy recycling.

Research on the Solar Water Cooler

A solar water cooler that uses solar energy directly or indirectly to cool the water consists of a cool water storage tank, a condensing wall, an auxiliary refrigeration device, with an insulating board dividing the cool water storage tank into an upper water-cooling tank and a lower water freezing tank. The system provides a solar water cooler with a dual-temperature cool water tank that reduces the water temperature to the minimum temperature of the day via heat dissipation, and the obtained minimum-temperature water is delivered directly for cooling purposes or delivered onto the condensing device as cooling water to improve the cooling efficiency. The auxiliary refrigeration device helps reduce the water temperature when the cooling water does not reach the required temperature for the air conditioner for refrigeration purposes. The major tasks of this study are to reduce the temperature of the cooling water to lower than the minimum temperature of the day and increase the required temperature of the air conditioner for refrigeration to save energy. With these two challenges solved, most areas in the world can use air conditioners with solar water coolers for cooling purposes, thus alleviating global warming and benefiting the whole world population.