Characteristics of two-phase flow heat transfer of R-22 and R-290 in horizontal circular small tube

Hydrocarbon refrigerants have been widely used to replace HFCs. As hydrocarbon, R- 290 has no ODP (Ozone Depletion Potential) and negligible GWP (Global Warming Potential). This paper presents flow boiling heat transfer in small tube with R-290 and R-22. The test tube has inner diameter of 7.6 mm and length of 1.07 m. In order to determine the heat transfer coefficient, experiments were carried out for heat fluxes ranging from 10 to 25 kW/m2K, mass fluxes ranging from 204 to 628 kg/m2s, and saturation temperatures ranging from 1.87 to 11.9o C. The study analyzed the heat transfer through the local heat transfer coefficient along the flow under the variation of these different parameters. In comparison with R-22, R-290 provides higher heat transfer coefficients. In the prediction of the heat transfer coefficients of R-22 and R-290, the correlation of Shah (1982) and Choi et.al. (2009) best fitted the present experimental result, respectively

Effects of two-phase flow friction factor correlations on the optimal pressure drop-martinelli parameter pair in a mini-channel

Substantial research has been completed with more on-going on the flow pattern and heat transfer associated with two-phase flows. Discrepancies reported may have been as much as agreements, due to the different models, approaches, flow regimes, correlations, and new working fluids being utilized. This paper reports the outcome of a study to look at the effects of applying two different friction factor correlations on the simultaneous minimization of the pressure drop and Martinelli parameter under optimized flow rate and vapor quality, using genetic algorithm. The homogeneous model is assumed with ammonia as the working fluid, the coolant being environmentally friendly and having recently discovered as a potential replacement for the current refrigerants in micro and mini-channels. Results show that significant differences in the frictional pressure drop and Martinelli parameter arise due to the different correlations used, and this is only the outcome from two different correlations currently being considered by researchers in pressure drop analysis for two-phase flows in mini-channels. Thus, absolute agreement is indeed not possible between theoretical, experimental, and numerical work in view of the many different available correlations being utilized today with differences between 10 to 100 percent that has already been established

Modeling of the minimized two-phase flow frictional pressure drop in a small tube with different correlations

The major parameters of interest in heat transfer research are the refrigerant charge, pressure drop, and heat transfer capacity. Smaller channels reduce the refrigerant charge with higher heat transfer capability due to the increased in surface area to volume ratio but at the expense of a higher pressure drop. Differences between the predicted and experimental frictional pressure drop of two-phase flow in small tubes have frequently been discussed. Factors that could have contributed to that effect have been attributed to the correlations used to model the flow, some being modified from the originals developed for a macro system. Experimental test-rigs have varied in channel geometry, refrigerant type, and flow conditions. Thousands of data have been collected to find a common point among the differences. This paper reports an investigation of four different two-phase friction factor correlations used in the modeling of the frictional two-phase flow pressure drop of refrigerant R-22. One had been specifically developed for laminar flow in a smooth channel, another was modified from a laminar flow in a smooth pipe to be used for a rough channel, and two correlations are specific for turbulent flow that consider internal pipe surface roughness. Genetic algorithm, an optimization scheme, is used to search for the minimum friction factor and minimum frictional pressure drop under optimized conditions of the mass flux and vapor quality. The results show that a larger pressure drop does come with a smaller channel. A large discrepancy exists between the correlations investigated; between the ones that does not consider surface roughness and that which does, as well as between flow under laminar and turbulent flow conditions

Heat Transfer Coefficient Characteristic Study of Natural Refrigerant with Substitute for R-134a

The wide-spread use of halocarbon refrigerants are making negative impact on Earth. Natural Refrigerant, such as hydrocarbon, is one alternative of several option to use. Mixing hydrocarbon are develop to improve the heat transfer characteristic. For example is, Musicool-134 (MC-134) is a mixture with two major substance of propane and iso-butane. The experimental apparatus is using a microchannel with a diameter of 0.5 mm and length of 0.5 m. The evaporative process was conducted in the experiment. The result of the experiment is that if the high coefficient value then the heat flux value is also high

Rheology Characteristics and Critical Velocity of Particle-laden Flow Affected by Three-lobed Spiral Pipe

The use of piping systems for fluid transportation is increasing because it is considered the most effective method. Newtonian and non-Newtonian fluid flows are suitable for piping systems, and non-Newtonian, particle-laden fluids are more complex due to various factors. Deposition is one of the problems that must continue to be investigated because of the effects of flow efficiency. The purpose of this study was to investigate the performance of the three-lobe spiral pipe effect. Working fluids in several variations of concentration weight (Cw 20%, 30%, and 40%) were used. Test pipe with a length of 1550 mm and consisting of spiral pipe P/Di = 7 and a circular pipe with an inner diameter of 25.4 mm were used. The circular pipe was used to investigate the rheological workings of fluid. Both pipes were used to investigate the particle effects. Using scanning electron microscopy, 1-?m to 5-?m slurry particles were obtained from the mud eruption source at Semau Island, Kupang, Indonesia. The critical velocity value of the spiral pipe was lower than the circular pipe, so the spiral pipe is highly effective for slurry transportation

Flow boiling heat transfer and pressure drop of propane in smooth horizontal minichannels

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.This study examined convective boiling heat transfer and pressure drop in horizontal minichannels using propane. The local heat transfer coefficients and pressure drop were obtained for heat fluxes ranging from 5-20 kW m-2, mass fluxes ranging from 50-400 kg m-2 s-1, saturation temperatures of 10, 5, and 0°C, and quality up to 1.0. The test section was made of stainless steel tubes with inner diameters of 1.5 mm and 3.0 mm, and lengths of 1000 mm and 2000 mm, respectively. The section was heated uniformly by applying an electric current to the tubes directly. The present study showed an effect of mass flux, heat flux, inner tube diameter, and saturation temperature on heat transfer coefficient and pressure drop. The experimental results were compared against several two-phase heat transfer coefficient and pressure drop prediction methods. A new boiling heat transfer coefficient correlation based on the superposition model for propane in minichannels was developed with a mean deviation of 8.27%

Thermofluids on Renewable Energy, Refrigeration and Air Conditioning, and Flame and Combustion

Increasingly limited sources of fossil energy are driving people to seek alternative energy resources. The use of photovoltaic (PV) and biogas for electric power generation continues to be accompanied by efforts to improve their system performance. Electrical ratings on PV systems, and the design of the digester in the biogas combustion process, are two of the relevant issues presented in this edition. Absorption cooling systems for buildings with solar power is one type of environmentally friendly system. In addition, the use of the natural refrigerant propane and a small channel can provide a higher heat transfer coefficient. In the heating and cooling process, the heat transfer characteristics are changed due to the phase change of the working fluids or material. Therefore, research on phase change material or working fluids has become an important way to support energy savings. Adsorption cooling systems that work with certain materials have shown better system performance, are environmentally friendly, and are energy-saving. System performance is determined by the properties of the material or the working fluid; it can be improved by modifying the serial or parallel stages of the process, which can be implemented in the dehumidification process. The pyrolysis process is another example of an application of thermofluids that uses flame and combustion; here, a carbonaceous solid is thermally degraded via heat in the absence of oxygen. For safety in flame and combustion, controlling the oxygen concentration can reduce the propensity for ignition and lower the fire propagation rate. Related applications on the engine and controlling the conditions of combustion in the engine room can improve engine performance

Research Frontiers in Energy, Materials, Production, and Transportation

The growth of research in various areas highlights the increasing needs of human life, such as in the fields of energy, materials, production, and transportation. Research in the field of fluid flow for energy savings is now very advanced, and research on the fluid flow pattern with a micro-scale is performed to obtain a high heat transfer with a low pressure drop. The use of microorganisms, biomass, and the Organic Rankine Cycle (ORC) is employed to stimulate heat transfer and fluid flow to produce energy through a more efficient and more environmentally friendly process. Furthermore, research on the designs and processes of air-conditioning systems is essential in view of energy consumption, which has exhibited a significant rise. Air conditioning is included in the future of transportation, namely electric cars, to achieve energy efficiency in vehicles. In addition to vehicle systems, attention should also be given to the precision of the routes and schedules of vehicles, particularly for public transport, so research on transportation modeling has also become very important. Another increasing requirement, which in the past has not been very well thought out, is the level of human comfort in driving. The challenge is to align the needs of driving comfort with energy efficiency requirements. The effort to reduce fuel consumption is also applied in marine transport modes by reducing the drag of ships. Moreover, cost efficiency related to energy consumption is an important issue in the production process. The management of manufacturing processes, including the production arrangement layout area, will greatly affect efficiency. This special edition presents the current manufacturing research in relation to various technologies associated with materials, automation, semiconductor, and nano devices

Optimization of the Friction Factor and Frictional Pressure Drop of R22 and R290

Today, the air-conditioning and refrigeration industry is still searching for environmentally friendly refrigerants that could replace hazardous, ozone-depleting coolants – refrigerants that behave similarly, if not better, than the present ones. The present study examines optimization of the frictional pressure drop of R22 and R290 using genetic algorithm. Outcomes are compared against the measured pressure drop obtained from a horizontal 7.6 mm channel with a length of 1.07 meters. Three equations have been used for calculating the Darcy friction factor and two-phase flow pressure drop for both laminar and turbulent flow regimes in smooth and rough tubes. The effects of the different correlations for the friction factor and pressure drop utilized are demonstrated. The results illustrate that the differences between values of the Darcy friction factor are very small for the two refrigerants examined, with the frictional pressure of R-290 higher than R-22. Use of a smaller channel induced a much higher frictional pressure drop, as well

Performance of natural refrigerants in two phase flow

The search for alternative environmentally friendly refrigerants have never been so crucial with the increasing demand for effective cooling of increasing miniaturization of our heat exchanging devices in the ever expanding air-conditioning and refrigeration industry. Although propane (R290) and ammonia (R717), natural refrigerants, have been around for decades, their two-phase thermal performance in small channels has yet to be fully investigated. Predictions of the heat transfer using correlations developed based on past experimental data have shown poor agreements, with more correlations being developed to date. This research was done to investigate the optimized conditions for the two-phase boiling heat transfer coefficient of R290 and R717 where the contributions from nucleate boiling and forced convective are represented explicitly. Multi-objective Genetic Algorithm (MOGA) is utilized for the simultaneous maximization of nucleate boiling and forced convective, two conflicting phenomena-the former generally significant in the low vapor quality region while the latter in the high quality region. A superposition correlation is used as it sums up both contributions. Two phased-out refrigerants, R134a and R22 are also being research here for comparison purposes. The range of MOGA design parameters set for mass flux, G, is between 100-300 kg/m2.s, heat flux q between 5-30 kW/m2 and vapor quality, × for 0.0009-0.9. The optimization is done for 3 mm channel diameter with saturation temperature at 10˚C. The optimized results showed a strong contribution of each nucleate boiling and forced convective for R717 with increasing vapor quality, compared to the other three refrigerants. The optimized value of the total heat transfer coefficient for R717 could reach up to 90 kW/m2.K and for R290 up to 12 kW/m2.K compared to R134a and R22 at 6 kW/m2.K and 5 kW/m2.K respectively. At lower vapor quality, the nucleate boiling contributes more to the total heat transfer coefficient, and suppressed due to forced convective as the vapor quality reaches middle range. The theoretical results indicate the potential of R717 and R290 as replacement refrigerants for R22 and R134a with further verifications to be done with correlations not using the superposition method