Freon Refrigerants Research Articles

New adsorbent materials based on PILs for Freon refrigerants.

The development of refrigerant adsorbent materials is not only essential for enhancing the efficiency of refrigeration systems but also plays a pivotal role in environmental conservation and addressing global warming challenges. However, traditional adsorbent materials are often limited in widespread applications in industrial scales due to various disadvantages, such as low adsorption efficiency, difficulties in desorption, and poor reusability. In this context, three distinct PILs, P[EVIM][PF6], P[BVIM][PF6] and P[HVIM][PF6], were synthesized and characterized. In addition, their structure as well as adsorption capacities towards three different Freon refrigerants (R12, R22 and R134a) were explored. The results indicated that the synthesized PILs had high thermal stability and exceptional adsorption capabilities, with P[EVIM][PF6] demonstrating the best adsorption performance. These PILs consistently maintain a stable saturated adsorption capacity throughout nine consecutive adsorption-desorption cycles, and the desorption rate of the adsorbent tubes consistently exceeded 96%. Thus, the superior recyclability of these PILs was verified. These PILs provide a promising route for efficient adsorption of Freon refrigerants, highlighting their potential significance in pertinent industries and environmental conservation efforts.

The effect of relative humidity on multicomponent organic vapor adsorption on composite beds with micro-fibrous entrapped activated carbon

Composite bed involves an alternative technique in which a layer of micro-fibrous entrapped composite material is added at the downstream end of a conventional fixed bed to strengthen the mass transfer process. In this study, our purpose was to compare the ability of composite beds to remove volatile organic compounds (VOCs) and Freon refrigerants with conventional fixed beds and analyse the effect of relative humidity (RH) on multicomponent organic vapor adsorption on composite beds. This would be used to guide the design of composite beds and their application in air purification. A series of micro-fibrous entrapped activated carbons (MFECs) were prepared using the wet layer paper-making/sintering technologies. The 1,1,1,2-tetrafluoroethane (R134a) and C6H6 breakthrough curves and times on composite beds were systemically evaluated under dry and wet conditions. Results show that under dry condition, due to the enhanced mass transfer, the R134a and C6H6 breakthrough times on composite beds were longer than on fixed beds. Under wet conditions, due to the water vapor competitive adsorption and the difference in organic vapor boiling point, the composite bed prolonged the C6H6 breakthrough time but weakened the R134a breakthrough time. Multicomponent competitive adsorption process (R134a/C6H6) under wet conditions was revealed and divided into six stages including Co-adsorption, H2O and R134a breakthrough, R134a desorption, R134a and H2O adsorption equilibrium, C6H6 breakthrough, and dynamic adsorption equilibrium. These findings indicated that composite beds may improve the breakthrough time of low-concentration C6H6 and lengthen the service life of conventional fixed beds at any RH, thereby displaying potential for use as an application in air purification.

Investigations of In-Plane Fluidelastic Instability in a Multispan U-Bend Tube Array—Part II: Tests in Two-Phase Flow

Abstract Tests to study fluidelastic instability (FEI) in an array of U-bend tubes were recently completed in the multispan U-Bend test rig at Canadian Nuclear Laboratories. These tests were sponsored by the Electric Power Research Institute and were designed to study in-plane fluid elastic instability of steam generator tubes in two-phase cross flow. This instability mechanism was first observed in previous experiments by Atomic Energy of Canada Limited. This mechanism was not thought to be a serious practical concern until 2012 when it caused severe damage to tubes in a new replacement steam-generator in a nuclear power plant in the United States. In this study, tests were conducted both with flows of air and two-phase liquid/vapor Refrigerant 134a. The tube bundle consisted of 22 flexible U-bend tubes supported by a configurable flat-bar arrangement. Testing focused on the effects of support geometry and tube-to-support interaction. Data were recorded from 33 dynamic signals from accelerometers, displacement probes, force transducers, and void-fraction probes. Part I of this two-part series presented results of air tests. Part II presents results of tests using two-phase Freon refrigerant (R-134a) as the working fluid.

Deposition of nano-scale polymer film on micro-fins to enhance the film-wise condensation of very low surface tension substances

Dropwise condensation is extremely difficult to accomplish through the nanostructured surfaces for very low surface tension substances, such as the Freon refrigerants. To further improve the laminar film condensation heat transfer of the substances with very low surface tension, rely solely on the super hydrophobic layer might not work. In this work, a three dimensional micro-finned tube was fabricated and a layer of polymer coating was deposited outside the fins. Condensation of two substances, R1234ze(E) and R134a, were investigated at saturation temperature 30 and 40℃. Under the coupling effect of coating and fins, the condensing heat transfer coefficient can be up to 28 times larger than the smooth tube and the value can reach 43 kW/m2K at heat flux 20 kW/m2. In the lower heat flux, it can be 150% higher than the same finned tube without polymer coating. As the condensing heat transfer enhancement with only fin structure modifications would soon reach its limit, it should have a good application prospect for the micro-fins with surface treatment.

Novel energy station by natural fluid CO 2

Novel energy station by natural fluid <scp> CO ₂ </scp>

Refrigerant selection for different cryogenic temperatures

Compression refrigeration is widely used in chemical processes to cool process streams to below-ambient temperatures. A single stage (one evaporator, one compressor, one condenser and one expansion valve) can be used down to temperatures of about 40 °C using several refrigerants such as R134A, ammonia and propylene. Lower temperatures require multiple stages using progressively lower-boiling refrigerants in each stage.The selection of the “best” refrigerant involves economic, environmental, safety and political issues as well at technical performance and economics. The Freon refrigerants are safe but impact the ozone layer. Ammonia and propylene present safety concerns due to toxicity and flammability. The purpose of this paper is to explore how the desired temperature of refrigeration affects the refrigerant selection and the number of stages with only economic monetary considerations taken into account. The economic objective function considers both compressor energy costs and capital investment in compressors and heat exchangers.

Experimental investigation of a two-phase closed thermosyphon charged with hydrocarbon and Freon refrigerants

Two-phase closed thermosyphons (TPCTs) are simple, efficient, and low cost heat exchangers. They have been explored for use in the renewable energy resource utilization marker and low grade thermal energy heat recovery systems. Freon R134a has been extensively used in refrigeration systems and researched as a working fluid of TPCTs; however; it has high global warming potential and operating pressure. In this paper, an experimental investigation of the performance of TPCTs charged with eight working fluids: R134a, R601, R245fa, R600a, R1234ze, R152a, R245fa/R152a, and R601/R245fa have been carried out. The experimental results showed that R245fa/R152a offered the best performance in maximum heat transfer rate. R134a outperformed the other pure working fluids, while R600a and R1234ze had close performances to that of R134a. R245fa showed marginal improvement at higher operating temperatures. The predictions of six evaporation heat transfer coefficients (HTCs) correlations, including Imura, Shiraishi, Labuntsov, Kutateladze, Cooper, and Rohsenow were compared with the experimental results. In the five constant coefficients and powers correlations, the Shiraishi and Cooper correlations had superior accuracy. The coefficients and powers of the Rohsenow correlations fitted based on the experimental data, while they had the best accuracy. Nusselt and Hashimoto-Kaminaga correlations were chosen to predict the condensation HTCs. Both of them tend to over-predict the condensation HTCs in low heat fluxes while under-predicting in high heat fluxes. The experimental results had greater agreement with Hashimoto and Kaminaga correlations.

Experimental Performance of a Two-phase Closed Thermosyphon Charged with Hydrocarbons and Freon Refrigerants for Renewable Energy Applications

Experimental performance investigation of a two-phase closed thermosyphon (TPCT) charged with eight working fluids: R134a, R601, R245fa, R600a, R1234ze, R152a, R245fa/R152a and R601/R245fa has been carried out. The TPCT was made of 3 m long smooth copper pipe with an di of 40mm. The evaporator section was immersed in the thermostatic water bath and the condenser section was cooled by recycled water. The experimental results show that R245fa/R152a offers the highest heat transfer rate Q, and R600a and R1234ze performance closely to R134a. Cooper and Rohsenow pool boiling HTC correlations were chosen to compare with the experimental results, which have good agreement with the measurements and the average errors are 23.1% and 16.6% respectively. Nusselt and Hashimoto and Kaminaga correlations were chosen to predict the condensation HTCs. Compared with the measurements, both tend to over predict the condensation HTCs in low tb (Q) and under predict the HTCs in high tb (Q). And Hashimoto and Kaminaga correlation offers better agreement.

Thermal Analysis and Design Applications of the Spiral Groove Tubes in Condensers

In this paper, condensation mechanism of the Freon refrigerants outside spiral grooved tube is discussed. The heat transfer coefficient of Freon refrigerants condensation outside spiral grooved tube is obtained. A calculation example of heat transfer coefficient on the tube bundle of condenser with baffle bars is presented. It shows the excellent thermal performance of the spiral groove tubes compared to smooth tubes.

다양한 냉매를 적용한 초임계 히트펌프의 성능 비교

In this paper, the cycle performance analysis for the COP of supercritical heat pump using various refrigerants is presented to offer the basic design data for the operating parameters of the system. The working fluids are R134a, R22, R32, R290, R600, R600a, R1270 and R744. The operating parameters considered in this study include superheating degree of evaporator, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature in the supercritical heat pump system. The main results were summarized as follows : Superheating degree, temperature of gas cooler inlet and outlet, compressor efficiency and evaporating temperature of supercritical heat pump system have an effect on the COP of this system. With a thorough grasp of these effect, it is necessary to design the supercritical heat pump using R134a. And, in comparison of COP of supercritical heat pump using various refrigerants, R32 and R600 is the highest, and R744 is the lowest among other refrigerants. From these results, it is confirmed that the COP of supercritical heat pump using R744 is higher than that using freon refrigerants such as R32 and R134a.

친환경 프레온 냉매를 이용하는 단압축 단팽창 냉동시스템의 성능예측

In this paper, cycle performance analysis of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants is presented to offer the basic design data for the operating parameters of the system. Alternative freon refrigerant for freon refrigerant R22 were used as working fluids in this study. The operating parameters considered in this study included evaporation temperature, condensation temperature, subcooling degree, superheating degree, and mass flow rate ratio of inter-cooler. The main results were summarized as follows : The COP of two-stage compression and two-stage expansion refrigeration system increases with the increasing subcooling degree and mass flow rate ratio of inter-cooler, but decreases with the increasing evaporating temperature, condensing temperature and superheating degree. Therefore, subcooling degree, mass flow rate ratio of inter-cooler of two-stage compression and two-stage expansion refrigeration system using alternative freon refrigerants have an effect on COP of this system.

Study on open-cycle carbon dioxide refrigerator for movable mine refuge chamber

For a movable mine refuge chamber, the refrigeration system is important to remove miners' body heat and the heat input from the hot outside environment. The refrigeration cycle has been changed from closed cycle using traditional Freon refrigerant to open cycle using high pressure carbon dioxide. The open cycle refrigerator has no compressor and it consumes no electricity. The open system is composed of a Joule–Thomson (JT) valve, an evaporator, a capillary heat exchanger, a pneumatic blower and several connecting tubes. For the evaporator, a stainless steel heat exchanger as well as a smooth tube heat exchanger were designed and tested and compared with a conventional finned tube copper heat exchanger. The tests show that the performance of cooling and dehumidification is nearly the same for the three heat exchangers. Because the stainless heat exchanger has higher strength and lower cost than the two others, it might be the best choice in actual applications. A long capillary tube heat exchanger is used to decrease the carbon dioxide pressure from around 20–35 bar to 5 bar, and at the same time the gas is kept above a temperature of 10 °C by making use of the sensible heat.

대체 프레온 및 자연 냉매를 이용하는 이원 냉동시스템의 성능 예측

In this paper, cycle performance analysis of cascade refrigeration system using alternative FREON refrigerants and natural refrigerants are presented to offer the basic design data for the operating parameters of the system. The operating parameters considered in this study include subcooled and superheated degree, and condensing and evaporating temperature, temperature difference of cascade heat exchanger in cascade refrigeration system. The COP of cascade refrigeration system increases with the increasing subcooled degree, but there is no significant changes with the increasing superheated degree. The COP of cascade refrigeration system depends on evaporating and condensing temperatures of cascade heat exchanger. Therefore, subcooled degree, evaporating and condensing temperature of cascade heat exchanger using alternative FREON refrigerants and natural refrigerants have an effect on the COP of this system. In this paper, COP of cascade refrigeration system using (R23 / R290), (R23 / R600), (R23 / R600a), (R23 / R717), (R744 / R404A) are higher 20 ~ 36 % than (R23 / R22), using R23 for low temperature system and R22 for high temperature system.

Analysis of Refrigerants Properties and Alternative

With the question of Ozone Depression Potential and Global Warming Potential popping out day by day, the Freon refrigerant alternative has become one of the current research contents of refrigerant. Based on the given Freon refrigerant R22, R134a and natural refrigerant CO2, the differences of their properties were compared, and the relevant alternative refrigerants conducted an investigation. The results show that the natural refrigerant CO2 instead of Freon refrigerant has good application prospects; it provides basic data to develop new products, which enhance the COP of air conditioner and heat pump.

Study of Liquid Desiccant Air Conditioning System Combined with Cognitive Sensing Network

The Application of Liquid Desiccant Absorption Air Conditioning System Is Booming; Governments, Investors, Researchers, Manufacturers, Resellers and Customers Are All Focusing on the Concepts of Environment Protection and Energy Saving, it Can Utilize Low Cost Energy as Regeneration Heat Source, for Example Solar Energy, Industry Waste Heat, Ground Heat. the System Utilizes Intelligent Wireless Sensor Network to Control the Air Conditions’ Operation, Optimize its Performance. on the other Side, the System Gets Rid of Freon Refrigerant, Doesn’t Create Pollution, Solved the both Energy and Environment Issues Effectively. the Paper Analyzed the Characteristics of the New Air Conditioning System, Tabled a Proposal of Combining the New Air Conditioning System with Ubiquitous Sensor and Pervasive Computing Platform, Discussed its Feasibility, Supply a Theory behind the Design.

Performance Characteristics of Absorption Cooling Cycle Operated by Low Thermal Potential Energy Sources

The possibility is investigated of using freon refrigerants and organic solvent systems in absorption refrigeration installations, utilizing low thermal-potential energy sources, for refrigeration and direct contact cooling to temperatures of or below 0°C. A detailed thermodynamic analysis by means of a simulation model of the cycle for several refrigerant-absorbent systems has delineated the operating range and dependence of the variations of the coefficient of performance and of the circulation ratio upon generator and condenser temperatures. The performance characteristics of freon - dibutyl phthalate and freon - dimethyl ether of tetraethylene glycol systems were compared.

Calculated Characteristics of a Hydraulic Refrigeration System

An unconventiona l cyclic type of refrigeration system is described whjch has only liquid pumps as its moving parts. A first-approximation type analytical model is presented in which the flow is considered one-dimensional, although two-phase in some parts of the system. The conventional friction factor is used to account for fluid friction and other losses are simply but appropriately modeled. Calculations are implemented in a digital computer program which solves the modeling equations serially around the (two) fluid loops, using iteration as necessary. Refrigerant properties are used with locally correct values as retrieved from property functions provided to the main program. The calculated performance of the hydraulic refrigeration system (HRS) using Freon 114 and water as the fluids, and with a capacity of approximately 3 tons (10.55-kW), is presented extensively graphically as an example of the characteristics of an HRS. Calculated results for the HRS in 10-ton (35.16-kW) and 100-ton (351.6-kW) sizes using Freon 114 are presented less extensively, and performance is briefly given using certain other Freon refrigerants. The calculations indicate that the HRS is capable of producing refrigeration at 45 °F (7.2°C) with a COP better than obtainable with conventional refrigeration systems. A cf CD COP d d D / F g h K m p p

Thomas Midgley and the Politics of Industrial Research

The conventional distinctions between “practical” and “scientific” research and development can be misleading. The experience of Thomas Midgley, Jr., at the General Motors Corporation in the three decades before World War II, and especially his critical role in the development of “antiknock” gasoline additives, freon refrigerant, and synthetic rubber, illustrate this fact. Dr. Leslie demonstrates that the management of corporate research and development, especially as that management affects uniquely talented individuals whose interests do not necessarily reflect the immediate needs of the company as seen by management, is basic to success. To solve such problems as they arose, Charles F. Kettering, himself a sympathetic scientist as well as distinguished inventor, worked closely with chief executive Alfred P. Sloan, whose genius for solving managerial problems matched the scientific genius of the most brilliant men in the General Motors laboratories.

The hydrolysis of halocarbon refrigerants in freeze desalination processes part II. Theoretical prediction of hydrolysis rates and comparison with experimental data

A theoretical model has been developed for the calculation of the hydrolysis rate constant of freon refrigerants. The model is based on the assumption that the rate determining step in the hydrolysis of a halocarbon is the primary ionization of the neutral molecule to a carbonium ion and a halide ion. The theory includes the effects of hydration of ions as well as the effects of the dielectric constant and ionic strength of the solution. Comparison of the theory with experimental hydrolysis rate constants for Freon 21 (CHCl 2F), Freon 31 (CH 2ClF) and Freon 114 (CClF 2CClF 2) gives excellent agreement with three adjustable parameters, the Arrhenius collision frequency, the hydration energy of the carbonium ion and the ionic distance of closest approach. The hydration energy is the controlling value in the model and the best fit to the data is obtained for a value of 115 kcal per mole. This value is the electrostatic equivalent of five water molecules of hydration at a separation distance of 2.2 angstroms. The model can be used to predict the hydrolysis rate constants of other refrigerants which are of interest to freeze or hydrate desalination processes since convenient semi-empirical methods for predicting the required thermodynamic and molecular parameters for the model can be utilized in the absence of tabulated data.

Refrigeration for Photomultipliers

A closed-cycle mechanical refrigeration system has been adapted to cool photomultipliers automatically. Temperature is adjustable between +50 degrees and -55 degrees C and is stable to within +/-0.30 degrees C. An important feature of the design is the flexible connection to the cold box which allows extensive freedom of motion; this freedom is particularly important in astronomy where the cold box is mounted on the end of a telescope. Liquid Freon refrigerants have been used to cool photomultipliers for rocket flights. A brief description of two methods is given.