Amount Of Refrigerant Research Articles

Оценка времени захолаживания криогенного бака азотной парожидкостной смесью

At present, there exists a trend for spacefaring countries to use methane as fuel for the first stages of launch vehicles. Russia is currently developing a promising launch vehicle known as Amur LNG. However, due to methane being a hazardous (flammable and explosive) substance, it is poorly suited for fuel tank strength tests conducted using existing equipment. In this regard, we face an urgent issue of developing a safe method for simulating liquid methane temperature during strength testing of methane tanks. We propose to cool the tank with a nitrogen vapour-liquid mixture. To estimate cooling time for a cryogenic tank treated with a nitrogen vapour-liquid mixture as per the method proposed, along with determining the amount of refrigerant to be used, we solved its thermal state problem using the method of isothermal nodes. This approach may also be used for oxygen tanks.

Analisis Kinerja R290 sebagai Pengganti R32 pada Unit AC-Split Kapasitas 9,000 Btuh/hr

R290 is a type of natural refrigerant that has ODP = 0 and GWP = 4. While R32 from synthetic materials has ODP= 0 and GWP = 675 both are refrigerants used in Split AC. With this high GWP, it can have a damaging impact on the atmosphere. The advantage of R290 is that it has a lower density compared to R32, which can save the number of fillings in the AC unit by ±30% of the previous amount of refrigerant in the same volume. R290/R32 was flammable with LFL= 2%/13% and UFL= 10%/33%. The purpose of this study was to analyze the performance of R290 as a substitute for R32 on an AC-split unit with a capacity of 9,000 Btuh/hr. The steps used in the test are that the AC unit is placed in an open room with ambient temperature around 32°/80°C. The test was carried out until it reaches the optimal and stable temperature, then data is collected. The results of data collection from the evaporator air temperature R290/R32 = 21.4°C/23.0°C, condenser air temperature = R290/R32= 35°C/38.5°C, suction pressure= 90 psig/130 psig and discharge 200 psig/420 psig. The test data were analyzed and calculated using the Mollier Chart software with the results = R290/R32 = refrigeration effect = 344.8/272.2 kJ/kg, compression work = 12.18/13.02 kJ/kg, COP = 28.3/20.9, compression ratio = 2.2/3.2, strong electric current 4.98/5.73 A. From the decrease in electric current of R290 obtained a savings of 13.3% was obtained when converted to electricity bill payment and get a profit of 45,886/month.

Comparison of optimization methods for the design and control of reactive distillation with inter condensers

Reactive distillation (RD) is a promising alternative that can produce high-purity Silane. However, it requires a large amount of expensive refrigerant to condense it. Therefore, this work assesses the feasibility of installing intermediate condensers at stages in the RD column to reduce the utility cost. Thus, RD columns with one and two Intermediate Condensers named RD-IC and RD-2IC are studied in addition to the RD column. A Simulated Annealing Algorithm (SAA) minimizes the total annual cost (TAC) of the RD, RD-IC, and RD-2IC. In contrast, a Mixed Integer Linear Programming (MILP) problem minimizes the utility cost. The solutions of each approach are compared, and the control performance of the best alternative is studied. Dual temperature control is applied for all alternatives, and it can stabilize the process and maintain the purities of the products against throughput and composition disturbances.

Cooling Performance Enhancement of a 20 RT (70 kW) Two-Evaporator Heat Pump with a Vapor–Liquid Separator

20 RT (70 kW) two-evaporator heat pump system was developed, manufactured, and tested to enhance the cooling performance using a vapor–liquid separator. In the proposed system, two evaporators are connected in series, and the refrigerant passing through the primary evaporator is separated into vapor and liquid using a vapor–liquid separator. The vapor refrigerant is passed to the compressor, whereas the liquid phase flows into the second evaporator. The amount of vapor refrigerant sent to the compressor can be adjusted through a needle valve opening (0%, 50%, and 100%). The influence of this parameter on the cooling performance was analyzed. The cooling performance tests were repeated five times to check repeatability. Data associated with the air and refrigerant sides were obtained, and the average coefficients of performance (COPs) were calculated. The average COP associated with the air side was approximately 5% lower than that pertaining to the refrigerant side owing to the heat loss. In terms of the air-side cooling performance, the average COP was 3.14, 3.40, and 3.68 when the valve openings were 0%, 50%, and 100%, respectively. The cooling performance when the valve opening was 100% was 17.2% higher than that for the valve opening of 0%. The findings demonstrated that the cooling performance of a heat pump can be enhanced using two evaporators and a vapor–liquid separator.

Refrigerant migration and oil sump viscosity change of R290 high-pressure rotary compressor during shutdown process

Propane (R290) has excellent thermophysical properties and development potential. The dynamic characteristics of R290 rotary compressors and room air conditioners have been studied mainly on the start-up and defrost processes. There is little research on the shutdown process. Unlike hydrofluorocarbons (HFCs), the density of liquid propane is lower than that of lubricant. It is difficult for propane to dissolve into the oil sump and downward after the refrigerant separation after shutdown. The shutdown state affects the distribution of refrigerant in the oil sump and the mixture viscosity of the restart-up, which is related to the compressor reliability. In this paper, an R290 room air conditioner system was built and the variations of system pressures, temperatures, and oil sump parameters of an R290 high-pressure rotary compressor with three different lubricants were measured after shutdown in two conditions. As the experiments indicated, driven by the refrigerant supersaturation (the difference between the actual refrigerant solubility and saturation solubility) resulting from the rapid pressure drop after shutdown, a large amount of refrigerant separated from the oil sump, and the refrigerant solubility dropped fast. As the compressor temperature decreased, the bottom viscosity reached a peak. For the low-temperature heating condition, the peak was about 120.4∼160.1mPa•s. However, when the degree of supersaturation decreased to a certain value, the refrigerant no longer separated out. There is always a solubility gradient of refrigerant in the oil sump of R290 high-pressure compressor after shutdown. Its size was related to the pressure drop and the miscibility of lubricants and refrigerants.

Thermodynamic Analysis of Industrial Cooling Systems with the Usage of Different Types of Evaporators: Experimental Study

Energy efficiency and the amount of refrigerant in heat exchangers used in cooling systems has recently been an important research subject. In this study, in order to compare and analyze different types of evaporators, industrial refrigerators were designed and in this context, test setups in accordance with TS EN ISO 23953-2 standard were produced. R290 (propane) was used as the refrigerant in the designed system. During the experiment, temperature-pressure measurements were taken at a certain point in the cooling system equipment of the products, which were cooled every minute, and test data were recorded. As a result of the data obtained from the experimental results, while the temperature difference of the air entering and leaving the evaporators was 6.797 ℃ in the first system using ½” tube diameter evaporator, it was calculated as 7.052 ℃ in the corrugated and hydrophilic coated second system using 3/8” tube diameter. In the experimental setups, the energy consumed in the first and second systems and the masses of R-290 refrigerant were measured as 24.64 kWh, 23.39 kWh and 700 grams, 430 grams, respectively. Consequently, it was calculated that the second system was 5.073% and 38.57% more efficient in terms of energy efficiency and the refrigerant mass used. Coefficient of performance values for the first and second systems were found as 2.807 and 3.013, respectively.

R-1233zd(E) 냉매를 적용한 유하액막식 증발 열전달 특성에 관한 실험적 연구

Along with the development of low global warming potential (GWP) refrigerants to prevent global warming, the development of a falling film type evaporator is required to reduce the charge amount of refrigerant in an evaporator. Unlike existing flooded evaporators, the development of a falling film evaporator using refrigerant is still in an incomplete state. In this study, factors affecting performance characteristics of falling film evaporation using R-1233zd(E) refrigerant were experimentally confirmed and effects of film Re and heat flux on heat transfer were investigated. As film Re of each tube increased, heat transfer coefficient also increased. It then converged after a certain film Re. The relationship between the heat flux and the heat transfer coefficient was examined.

Experimental study and simulation model of a direct expansion solar assisted heat pump to CO2 for water heating: Inventory, coefficient of performance and total equivalent warming impact

This work is a theoretical and experimental study about the refrigerant charge inventory in a CO2 Direct Expansion Solar Assisted Heat Pump to heating residential water. The effects of variation in the irradiation levels were analyzed for 72 experimental points, and a mathematical model was developed to predict the amount of refrigerant in several parts of the system. The conditions of the supercritical fluid and two-phase flow were considered, and eight void fraction correlations were tested. The model revealed that changes in the solar irradiation levels had a significant effect on the mass amount, and the accumulator was responsible for compensating these variations. Nevertheless, in percentage terms, the mass distribution remained practically constant in the heat pump components. The best results for mass prediction were obtained by the correlations of Hughmark and Filimonov, with an average error of 6.38% and 6.88% respectively. Considering a tolerance margin of ± 2%, Hughmark reached total precision in 19.7% of the predictions against 9.2% achieved by Filimonov, and all the tested correlations had 100% accuracy for a tolerance of ± 18%. A growth of around 0.3 kW/m2 in the solar irradiation produced an increase of 30% in Coefficient of Performance (COP) and a reduction of 20% in Total Equivalent Warming Impact (TEWI). Among the conditions analyzed, the best operating point occurred with a COP of 3.67, TEWI of 733 kg CO2-eq and a mass of 589.9 g, with an error of 8.54%.

Parameter study of Variation noise in outdoor of air conditioner

In the outdoor unit of a room air conditioner, the main factors that made it possible to vary the ability of cooling and heating are the development of BLDC motors, advances in inverter technology, and the development of refrigerant volume control technology. The main reason for this change in cooling and heating capacity is that it is possible to change the RPS of compressors. As the range of the compressor's RPS expands, so does the range of response to load variations. This is mainly based on the capacity of the high-pressure refrigerant produced by the compressor. When the compressor rotates at high speed or low speed, the difference in noise occurs depending on the difference in rotational speed. Of course, fans and motors also contribute to noise fluctuations, but the overall governing factor is the greater contribution of refrigerant from compressors and compressors. The refrigerant flows into the cycle configured in the outdoor unit and varies in speed and flow rate depending on the amount of refrigerant. This results in vibration and noise appearing in the form of radiations, resonances, solid sounds, resonances, and so on. There are several factors that can cause vibration or noise changes depending on the flow velocity and flow rate. In this paper, we selected reactance of compressor motors, mufflers directly connected to compressor discharge ports and accumulator at compressor inlet where fluid vibrations occur the most. First of all, reactance of motor responds quickly to load fluctuations and has a large instantaneous torque to instantaneous load fluctuations. The muffler, which is directly connected to the compressor discharge port, is the first Cavity where high-pressure gas meets, and can evaluate the concentration of kinetic energy that generates noise and improve the collection center to reduce fluctuating noise. The Accumulator is the part with the lowest temperature of refrigerant gas entering the compressor, and the rapid change in the flow path causes the most fluid to generate vibration and radiation of the structure. For this reason, we select three elements first. In this paper, we specifically describe the background of selecting three elements of an air conditioning outdoor unit for the variability of noise over RPS changes. We demonstrate that these factors can review the feasibility of the experiment, explain the results of the analysis, and possibility of reduce the variation noise.

A novel condenser with offset strip fins on a mini channel flat tube for reducing the energy consumption of a household refrigerator

The aim of the study is to reduce the amount of refrigerant and energy consumption of a household refrigerator by conserving the desired temperature inside the fresh food and freezer compartments. In this study, two novel condensers with different offset strip fin configurations on a mini-channel flat tube are used instead of a conventional wire-on-tube condenser. The impact of this novel application on the performance of the refrigerator is investigated experimentally by following the norms defined by IEC 62552:2015. The tests are conducted in a wide range of refrigerant charges (48–64 g) with three different capillary lengths (2800, 3300, and 3800 mm). Alternative couples of refrigerant charge and capillary length for the novel condensers are determined to decrease the daily energy consumption under the level of the original system with the wire-on-tube condenser. One of the aims of the study is achieved by 5.7% of energy-saving when one of the novel condensers is coupled with a 3300 mm length capillary tube and 50 g of refrigerant. The other aim of the study related with the environmental effect is achieved by reducing 10.7% of the refrigerant amount with the application of the novel condenser with offset strip fins on a mini channel flat tube.

Variable Refrigerant Flow in Air Conditioning of Buildings: System Configuration and Energy Efficiency

Variable Refrigerant Flow (VRF), also known as Variable Refrigerant Volume (VRV) refers to the ability of an air-conditioning (AC) system to control the amount of refrigerant flowing to multiple evaporators (indoor unit). This study evaluates the VRF system to its core, and how the system is more beneficial in terms of built environment than the traditional air-conditioning system. This type of type of system consists of a number of air handling units (possibly up to 48) connected to a modular external condensing unit. The refrigerant flow in the VRF system is varied using either an inverter-controlled variable speed compressor or multiple compressors of varying capacity in response to changes in the cooling or heating requirement within the air-conditioned space. With the help of these advanced compressor like the twin rotary compressor the metering device can be closed to controls the flow of refrigerant between the indoor and outdoor unit which helps in avoiding the overheating or overcooling of the space. VRF system also helps in covering the duct losses which is impossible to cover in traditional system as VRF system is ductless or minimum duct are used in the process.

Life Cycle Assessment of an Innovative Hybrid Energy Storage System for Residential Buildings in Continental Climates

With the aim of contributing to achieving the decarbonization of the energy sector, the environmental impact of an innovative system to produce heating and domestic hot water for heating demand-dominated climates is assessed is evaluated. The evaluation is conducted using the life cycle assessment (LCA) methodology and the ReCiPe and IPCC GWP indicators for the manufacturing and operation stages, and comparing the system to a reference one. Results show that the innovative system has a lower overall impact than the reference one. Moreover, a parametric study to evaluate the impact of the refrigerant is carried out, showing that the impact of the overall systems is not affected if the amount of refrigerant or the impact of refrigerant is increased.

Numerical and experimental study of the transient behavior of a domestic vapor compression refrigeration system – Influence of refrigerant charge and ambient temperature

In this work, two transient mathematical models are presented for simulating a vapor compression refrigeration system of domestic refrigerator using R134a. One, the thermal model, is based on the application of the first law of thermodynamics and the second, capacitive model, adds the evaluation of the refrigerant mass distribution in the system. An experimental procedure to calculate the thermal conductance and capacity of system components (compressor, condenser, capillary tube, evaporator, cabinet) is presented. Experimental data describing the transient behavior of the refrigeration system are also obtained to validate the simulation procedures. The domestic refrigerator studied is a vertical two compartments refrigerator. The simulation results follow the measured experimental trends and are very satisfactory when compared to the transient and time averaged experimental data. The maximum relative error obtained for simulated temperatures was about 5.65%. Parametric analyses were conducted to identify the influence of refrigerant charge and ambient temperature on the refrigeration system performance. The optimum refrigerant charge has distinct values regarding the operational condition of the system. In the pull-down operation the highest COP is attained for 105g and 140g of refrigerant for transient and the steady-state regimes, respectively. In the on-off operation the optimum refrigerant charges are 105g for transient operation (placing goods inside the compartments) and around 70g to 95g for stationary condition (without goods). Excepting for small refrigerant charges ~50g, the higher quantity of refrigerant during the entire system operation is in the evaporator. For low refrigerant charges, 50–70g, it is also shown a refrigerant migration between condenser and evaporator under the effects of thermal loads when compressor is turned on. Ambient temperature augmentation by 18°C decreases refrigerator COP without thermal load in 10% and 16% for pull-down and on/off operations, respectively. The presented experimental results are new and can be used by other researchers for validating their own simulation models. The developed models can considerably improve the design of domestic refrigeration systems by manufacturers.

Refrigerant Charge Optimization of Air Conditioning System with Hydrocarbon Refrigerant

Determination of the amount of refrigerant in a vapor compression refrigeration system requires several approaches depending on the design and installation of the piping on each refrigeration component. For chiller systems or other packaged systems that are already loaded with refrigerant and do not require piping installation in the refrigeration system, the amount of refrigerant that is loaded into the unit is based on testing at the factory. Optimization of the amount can be done when the test is carried out in the laboratory setting and the chiller is operated with the target capacity and the performance. However, for chillers that have been installed on-site and are not in the design condition, the amount of refrigerant that must be input varies greatly to obtain optimum conditions. In this research, we will calculate the amount of hydrocarbon refrigerant R290 that must be done to achieve the most optimum or efficient conditions, in the 56 TR capacity chiller system that is installed at the Makara Art Center, Universitas Indonesia. The use of refrigerants, especially the hydrocarbon type R290, is expected to have the least amount of refrigerant possible, so it is important to determine the lowest charging with the best efficiency. The chiller system is also installed with the addition of the LSHX component which in previous studies showed the possibility of decreasing the contents of R290The refrigerant charge reduction from its optimum amount decreases the system’s efficiency. The reduction of refrigerant charge of 3.3% results in COP decrease up to 3.9%. It is then imperative that proper charging as well as minimizing leaks is important to keep the chiller works at its maximum efficiency.

Performance assessment of a two-stage CO2 small scale MT refrigerator

F-GAS regulation has introduced important limitations in the use of refrigerants in the small size commercial refrigeration sector, with a maximum GWP=150 since 2022, forbidding the use of R404A. Among alternatives, there are propane, low-GWP HFC/HFO mixtures or pure HFOs: each of them can be considered as an option depending on the refrigerant charge limit for the application or by the total cost accepted by customer. In case of remotely connected units with potential refrigerant leakages, such as condensing units, the use of CO2 is considered as an option, due to the its safety indexes (no toxic and no flammable) which enables the use of larger amount of refrigerant. Being the CO2 refrigerant cycle trans-critical in warm climates, it may have low COPs and not fulfil the limits imposed by Ecodesign rules. In this paper, a condensing unit working with R744 is experimentally tested to assess the performance according to EN13215:2016. To limit high temperature at the compressor outlet, a two-stage system working with an inverter-driven hermetic rolling piston compressor is considered with intercooler and flash gas removal at intermediate pressure. It has been verified that seasonal energy performance ratio (SEPR) can be over the threshold value of 2.3 applied since 2018.

New refrigerants and system configurations for vapor-compression refrigeration.

The high global warming potential of current refrigerants in cooling equipment based on the vapor-compression cycle has triggered a major effort to find and implement more environmentally benign alternatives. Here, we review the basics of the vapor-compression cycle together with the safety, environmental, and thermodynamic constraints that have led to the current and next generation of refrigerants. The development of new fluids has focused on fluorinated olefins, known as hydrofluoroolefins (HFOs), and blends that contain HFOs. Many of these are slightly flammable, presenting trade-offs between safety and environmental considerations. Engineers also have options with a resurgence of the "natural refrigerants" (ammonia, carbon dioxide, propane, and isobutane). Innovative system designs that reduce the required quantity of refrigerant may allow a wider choice of refrigerants.

Effect of refrigerant/oil solubility on thermodynamic performance of the evaporator working with R600a and DME

Isobutane (R600a) and dimethyl ether (DME) as promising refrigerants have attracted wide attention. To better understand their evaporative performance in the presence of oil, the solubilities were measured for R600a and DME in squalane from 293.15 K to 348.15 K. The data was correlated by the NRTL model. A new pressure-enthalpy-vapor quality diagram, which is applied to pure refrigerant and refrigerant/oil mixtures with various circulating oil mass fractions, is presented based on the data. The critical vapor quality was found in the isotherm of the refrigerant/oil mixture, and it depends on the circulating oil mass fraction and refrigerant/oil solubility. The higher critical vapor quality, the greater contribution of the latent heat, which is beneficial for heat transfer. The enthalpy changes through an evaporator with and without taking into account the effect of oil, as well as the non-evaporated quantity of refrigerant at the evaporator outlet, were also analyzed. The enthalpy change ratio increases with an increase of superheat and decreases with an increase in mass fraction of circulating oil. The non-evaporated quantity decreases with an increase of superheat and increases with an increase in the mass fraction of oil circulation.

선박 수리업체의 냉매 사용량 조사

The Kigali protocol is a follow-up to the Paris protocol, which phases out the use and emission of HFCs. Korea belongs to the first group and should take action under the Kigali protocol. Among them, new ships equipped with refrigeration facilities or repair of existing ships cannot use regulated refrigerants and must use alternative refrigerants. However, in the case of ships, especially in repair, it is very difficult to grasp the actual situation, so the statistics or actual conditions are unknown. Therefore, this paper is to investigate and analyze the amount of refrigerant used for ship repair, and to present the basic data and the current status. The main results are summarized as follows. Existing large-scale repair shipyards in Korea have been converted to new construction projects. Therefore, there are about 80 repair shipyards in Korea, but most of them are very small, with several thousand tons or less. Investigating the use of refrigerants by ship repair companies shows that most of the old ships are repaired, so the refrigerants of R22 and R717 are the most commonly used. Based on the survey of the refrigerant use status of ship repair companies, the refrigerant consumption is estimated to be 43,940 kg.

Thermo-Economic Analysis of Vapour Absorption Refrigeration System for an Office

Human comfort is considered to be a very important aspect of the modern lifestyle, the more the favourable condition of the room the better and comfortable a person feels thus Air conditioning is now being considered as a must for buildings, offices and homes. The air conditioning system can be optimized and can be built specifically for the required conditions of the space by designing an energy efficient and environment friendly refrigeration system as the thermal energy produced by burning the fossil fuels causes high CO2 emissions in the environment. Finding the heat load calculation helps in reducing the cost of building and maintaining the system it also helps in effective designing of the refrigeration system. Thus, in this paper we are calculating the overall heat load of an office, the total heat load of people, ventilation and infiltration, for calculating the amount of refrigeration required in the office. This paper also aims to use the solar energy by using its thermal energy, which has zero ozone layer depletion potential and zero global warming potential. This paper would also deals with the idea about the economic constraints and the calculation of Solar based VARS to maintain a desired temperature in an office room having 5 occupants.

Double-feedback control with stepless variable speed driving technology by sensing refrigerant pressure and indoor temperature applied to air conditioning system

An energy-saving strategy of variable refrigerant volume (VRV) is proposed for air conditioning systems by using the stepless variable speed driving technology. This control technology is applied to the air cooled packaged water chiller unit (ACH) according to the change of environmental heat load to achieve the best amount of refrigerant in real time. This study designs a double feedback Stepless Variable Frequency and Variable Refrigerant Output (DFSVFVRO) for controlling ACH. The double feedback variable frequency control uses both temperature and the pressure sensors as feedback signals to the control board and the frequency of the compressor is regulated by the inverter. Experimental results indicate that the proposed variable frequency control method has a lower energy consumption compared with the conventional normal mode (N). In addition, the proposed double feedback mode (DF) has a lower energy consumption, and thus, it is with better energy efficiency. Furthermore, in the various experiments of proposed DFSVFVRO by comparing the cumulative energy consumption of DF mode with N mode, the DF mode shows an energy saving rate of at least 25%. It also verifies that the double feedback variable frequency control method has a better energy-saving benefits than that of the single feedback frequency.