Effect Of Evaporation Temperature Research Articles

Thermal performance evaluation of subcritical organic Rankine cycle for waste heat recovery from sinter annular cooler

The sinter cooling flue gas expelled from the end of an annular cooler was taken as the heat source of an organic Rankine cycle (ORC) system, and R123, R245fa, R600, R601 and R601a were selected as the working fluids of the ORC system. The effects of evaporation temperature and superheat degree of working fluid, as well as the pinch point temperature difference in the evaporator on the system thermal performance, were analyzed in detail. The results show that the system net output power and exergy efficiency for different working fluids first increase and then decrease with an increase in the evaporation temperature and decrease with an increase in the superheat degree and pinch point temperature difference. The change in pinch point temperature difference has no effect on the system thermal efficiency. For a given operational condition, the system thermal efficiency and exergy efficiency of R123 are the maximum, while the system total irreversible loss of R245fa is the maximum. When the evaporation temperature is greater than 110 °C, the system net output power of R600 is the maximum. The ORC system could obtain the maximum net output power and exergy efficiency through the adjustment of evaporation temperature of working fluid.

Simulation analysis of performance optimization of gas-driven ammonia-water absorption heat pump

The generator-absorber heat exchange ammonia-water absorption heat pump has a relatively high efficiency and the COP is improved by recovering internal heat. In order to resolve the problem that generator-absorber heat exchange effect becomes less obvious or even fails under the working condition of large temperature lift, a novel system is proposed to recover the rectification heat and absorption heat by solution split method. Compared with the method of using total strong solution to recover absorption heat after extracting rectification heat, the method of solution split avoids the problem of high temperature of inlet strong solution of the solution cooled absorber, and improves the internal heat recovery capacity of the system. When using solution split method to recover the rectification heat and absorption heat, the solution split ratio K has an important influence on the system performance. This paper will theoretically study the selection range of the solution split ratio K and the effect of evaporation temperature, cooling water temperature and generation temperature on the optimum split ratio K. Compared to the system that uses the total strong solution to recover the rectification heat and absorption heat, the performance of the novel system is significantly improved, and the novel system performance coefficient can be increased by up to 15.7%.

Thermo-economic analysis and multi-objective optimization of vapour cascade refrigeration system using different refrigerant combinations

A numerical investigation of energetic, exergetic, economic and environmental performances of a 50-kW cooling capacity cascade refrigeration system using four different refrigerant pairs, namely R41–R404A, R170–R404A, R41–R161 and R170–R161, has been carried out. Effects of evaporator temperature, condenser temperature, LTC condenser temperature and cascade condenser temperature difference have been studied parametrically. The COP and exergetic efficiency of the system are found to be maximum with R41–R161 refrigerant pair followed by R170–R161 for the same operating conditions. Genetic algorithm technique has been employed to carry out multi-objective optimization for the cascade refrigeration system using above-mentioned four refrigerant pairs to evaluate the optimal performances (for maximizing exergetic efficiency and minimizing the total plant cost rate) and the corresponding operating conditions. A set of non-dominated solutions have been obtained from the optimization, and then, TOPSIS method is employed to get the unique solutions for all four investigated refrigerant pairs. Better results in terms of optimum exergetic efficiency and the total plant cost rate are obtained using R41–R161 and R170–R161 refrigerant pairs compared to those obtained using R41–R404A pair.

Molecular Distillation-Induced Deacidification of Soybean Oil Isolated by Enzyme-Assisted Aqueous Extraction: Effect of Distillation Parameters

Soybean oil isolated by enzyme-assisted aqueous extraction (EAE) was subjected to molecular distillation-induced deacidification, and the effects of evaporator temperature, scraper speed, and feed flow rate on oil quality (acid value, color, peroxide value, p-anisidine value, tocopherol content, and fatty acid content) were evaluated to determine the suitable deacidification conditions. Fatty acid content was largely unaffected by evaporator temperature and scraper speed, while an increase of these parameters decreased tocopherol content as well as acid, peroxide, and p-anisidine values and resulted in Lovibond color deepening. The increase of feed flow rate had an opposite effect on the above quality indices. As a result, molecular distillation of EAE-produced soybean oil under suitable conditions (evaporator temperature = 180 °C, scraper speed = 220 rpm, feed flow rate = 4 mL/min) was found to afford a high-quality deacidified product in an environmentally friendly way.

Development of a high temperature heat pump system for steam generation using medium-low temperature geothermal water

To expand the application range of medium-low temperature geothermal water, a high temperature heat pump system with refrigerant injection technique for steam generation is developed. Four working fluids of R123, R141b, R245fa and R1234ze(Z) used in the high temperature heat pump cycle are analyzed and evaluated. Besides, the effects of evaporation temperature, injection ratio of the compressor and condensation temperature on the system performance are also discussed. The results of thermodynamic analysis indicate that the system obtains the optimal performance when uses R141b as working fluid. As the evaporation temperature is 55oC, the condensation temperature is 125oC and the flash evaporation temperature is 100oC, the COP of the system reaches 3.8 and the steam mass per kWh (MkW) is 1.4 kg/kWh for R141b.

Energetic and exergetic performance comparison of cascade refrigeration system using R170-R161 and R41-R404A as refrigerant pairs

A numerical study of cascade refrigeration system using two different refrigerant pairs, namely, R41–R404A and R170–R161 working under the same operating conditions has been presented in this paper. A computer code has been developed in Engineering Equation Solver software using the basic energy and exergy equations of cascade refrigeration system. Values of some of the important input parameters for the analysis have been taken from the literatures to carry out this simulation work. The effect of evaporator temperature on the basic performance parameters, such as COP, compressor power, total exergy destruction, exergetic efficiency has been computed. The analysis of the predicted results shows that for each evaporator temperature, an optimal point exists where the system shows maximum performance. An effective reduction of compressor work and total exergy loss is observed with R170–R161 system than those of the R41–R404A system. This eventually results in higher optimal COP as well as exergetic efficiency for R170–R161 system compared to R41–R404A system.

Preparation of Bi4Te3 highly oriented nanopillars array film with enhanced electrical properties

The Bi4Te3 films with well-ordered orientation and microstructure were successfully prepared on SiO2 substrate by a vacuum thermal evaporation deposition technique for the first time. We discussed the effects of evaporation temperature and substrate temperature on the phase and its well-ordered growth of Bi4Te3 films. The formation of Bi4Te3 phase is owing to the differences of the saturated vapor pressure. The thermoelectric transport properties of the Bi4Te3 films were investigated and the (00l)-oriented nanopillars array film has a better electrical transport performance, whose value of PF is 0.032 mWm−1 K−2 at 339 K, approaching twice that of the non-oriented ordinary film. The enhanced electrical properties of Bi4Te3 films could be achieved via the high-crystallinity well-controlled (00l)-oriented nanopillars array.

The Effect of Evaporation Temperature on the Structure and Conductivity of Thin Films Obtained by the Moving Meniscus Method from Nanodispersions of Silver Particles

The effect of temperature (23–58°C) on the structure and conductivity of thin films obtained by the moving meniscus method from nanodispersions of silver particles with sizes of 6.5–70 nm has been studied. It has been shown that an increase in temperature leads to an exponential decrease in the specific conductivity of the films, with their thickness varying nonmonotonically. In the case of “large” particles, an increase in temperature decreases the efficiency of their deposition onto a substrate. The reasons for the observed regularities have been discussed.

Energy and exergy analysis of vapour compression refrigeration system using selected eco-friendly hydrocarbon refrigerants enhanced with tio2-nanoparticle

The experimental study investigated the energy and exergy performance of a domestic refrigerator using eco-friendly hydrocarbon refrigerants R600a and LPG (R290/R600a: 50%/50%) at 0, 0.05, 0.15 and 0.3wt % concentrations of 15nm particle size of TiO2 nano-lubricant, and R134a. The effects of evaporator temperature on power consumption, coefficients of performance, exergetic efficiency and efficiency defects in the compressor, condenser, capillary tube and evaporator of the system were examined. The results showed that LPG + TiO2 (0.15wt %) and R600a + TiO2 (0. 15wt %) had the best of performances with an average of 27.6% and 14.3% higher coefficient of Performance, 34.6% and 35.15% lower power consumption, 13.8% and 17.53% higher exergetic efficiency, a total exergetic defect of 45.8% and 64.7% lower compared to R134a. The exergetic defects in the evaporator, compressor, condenser, and capillary tube were 38.27% and 35.5%, 49.19% and 55.56%, 29.7% and 33.7%, 39.1% and 73.8% lower in the system when compared to R134a respectively. Generally, the refrigerants with nano-lubricant mixture gave better results with an appreciable reduction in the exergy defect in the compressor than the pure refrigerants, and LPG + TiO2 (0. 15wt %) gave the best result in the refrigeration system based on energy and exergy analysis.

The viability of ultra low temperature waste heat recovery using organic Rankine cycle in dual loop data center applications

The Organic Rankine Cycle (ORC) is a promising technology for waste heat recovery in data centers due to its low-cost production of electricity, which can be used elsewhere in the data center. In this paper, an analysis is presented which assesses the effectiveness of ORC systems in repurposing data center waste heat energy from both thermodynamic and economic points of view. The starting point for the analysis is the development of a steady-state thermodynamic model for an ORC system consisting of an evaporator, expander, condenser, pump, and superheater. The model includes both first and second law analyses and is verified against existing data. The effect of evaporator temperature and working fluid type (dry, wet, and isotropic) on the efficiency of the system is examined. The ORC thermodynamic model is then integrated into a full server cooling system model. The efficiency of this system is determined for different operating fluids and thermodynamic conditions. Finally, a first-order economic analysis is performed using the results of thermal analysis and the information for price, installation and maintenance cost, provided by an ORC manufacturer. This work is unique in that the use of ORC in extremely low temperature applications has previously been considered to be of questionable benefit due to its low efficiency. This work highlights that there are clear benefits to be gained in ultra-low temperature applications, and is one of the first examples of ORC benefits in data center designs.For data center operating conditions, R134a and R245fa are identified as the optimum selections for the server coolant and ORC working fluid, respectively, but other environmentally friendly options are considered in the case that a data center operator is forced to swap out a fluid due to changes in environmental regulations. This gives data center operators greater insight into the performance of the system in the face of possible constraints. The analysis also considers the use of superheaters to increase the temperature at which the waste heat is recovered. This is often considered to be beneficial in waste heat recovery systems. However, the results show that while increasing the temperature at which the waste heat is recovered improves ORC system performance, the addition of superheaters in either the ORC loop or the server cooling loop results in an overall performance decrease due to the additional power required for their operation. A payback period of between 4–8 years for the use of ORC in data center environments is estimated.

Parametric Analysis and Comparison of Ejector Expansion Refrigeration Cycles With Constant Area and Constant Pressure Ejectors

In this work, parametric analysis of ejector expansion refrigeration cycles (EERC) with two different types of ejectors (constant area (CA) ejector and constant pressure (CP) ejector) is performed, and comparison of the results is presented. Effects of variation in operational parameters (condenser temperature, evaporator temperature, and cooling capacity) on coefficient of performance (COP), entrainment ratio (w), and pressure lift factor (Plf) are investigated. The range of variation for evaporator temperature, condenser temperature, and cooling capacity are −5 to 15 °C, 50–70 °C, and 10–80 kW, respectively. The ejector refrigeration cycle is simulated by ees software. The obtained results are validated by the experimental data available in the literature. The refrigerant R134a is selected based on the merit of its environmental and performance characteristics. The results show that the effect of evaporator temperature is much higher than that of condenser temperature on Plf. In contrast, the influence of condenser temperature on COP is much stronger than that of evaporator temperature. It is seen that COP and Plf of ejector expansion refrigeration cycle with constant pressure ejector (CP-EERC) are higher than those of refrigeration cycle with constant area ejector.

Effect of Evaporation Temperature on the Performance of Organic Rankine Cycle in Near-Critical Condition

Considering the large variations of working fluid's properties in near-critical region, this paper presents a thermodynamic analysis of the performance of organic Rankine cycle in near-critical condition (NORC) subjected to the influence of evaporation temperature. Three typical organic fluids are selected as working fluids. They are dry R236fa, isentropic R142b, and wet R152a, which are suited for heat source temperature from 395 to 445 K. An iteration calculation method is proposed to calculate the performance parameters of organic Rankine cycle (ORC). The variations of superheat degree, specific absorbed heat, expander inlet pressure, thermal efficiency, and specific net power of these fluids with evaporation temperature are analyzed. It is found that the working fluids in NORC should be superheated because of the large slope variation of the saturated vapor curve in near-critical region. However, the use of dry R236fa or isentropic R142b in NORC can be accepted because of the small superheat degree. The results also indicate that a small variation of evaporation temperature requires a large variation of expander inlet pressure, which may make the system more stable. In addition, due to the large decrease of latent heat in near-critical region, the variation of specific absorbed heat with evaporation temperature is small for NORC. Both specific net power and thermal efficiency for the fluids in NORC increase slightly with the rise of the evaporation temperature, especially for R236fa and R142b. Among the three types of fluids, dry R236fa and isentropic R142b are better suited for NORC. The results are useful for the design and optimization of ORC system in near-critical condition.

Comparison of transcritical CO2 refrigeration cycle with expander and throttling valve including/excluding internal heat exchanger: Exergy and energy points of view

The article compares four compression evaporative refrigeration cycles from energy and exergy points of view where carbon dioxide is considered as the working fluid. The four cycles are: (1) the cycle with expander, (2) the cycle with expander and internal heat exchanger, (3) the cycle with throttling and (4) the cycle with throttling and internal heat exchanger. In the cycles, effect of evaporation temperature and exhaust temperature of gas cooler on Coefficient of Performance (COP) and exergy efficiency are taken into consideration. From the energy and exergy points of view, the results indicate that using heat exchanger reduces COP and exergy efficiency of the cycle with expander while the use of heat exchanger in the cycle with throttling valve enhances the COP and exergy efficiency. The comparison between the four cycles reveals that the cycle with expander and without internal heat exchanger has the highest COP and exergy efficiency.

Thymol enrichment from oregano essential oil by molecular distillation

Abstract The objectives of this study were to obtain fractions enriched in thymol by molecular distillation of oregano essential oil and to evaluate their antioxidant properties. In addition, this operation was modelled considering the effects of evaporation temperature and feeding flow on thymol concentration in the residue fractions by means of artificial neural networks (ANN). All residue fractions had a higher percentage of thymol than the distillates. The thymol composition in the residue fractions reached values up to 2.4-fold higher than in oregano essential oil. Higher concentrations of thymol produced lower values for IC50 according to DPPH technique, indicating an increase in antioxidant properties. During the storage test, all the residue fractions analysed showed better peroxide, conjugated dienes and conjugated trienes values than distillates and OEO when they were used in sunflower oil samples. The results of storage stability showed that residues and BHT are very good antioxidants. The ANN created demonstrated good predictive ability for the operation of molecular distillation of oregano essential oil.

Performance Investigation of Joule–Thomson Refrigeration System with Environment Friendly Refrigerant Mixtures

The importance on energy conservation has resulted in new efforts to develop more efficient refrigeration systems for achieving low temperature. The Joule-Thomson (J-T) concept has been widely used for achieving low temperature. The overall performance of the refrigeration system is governed by the selection of the mixture composition and heat exchanger used. Therefore, an attempt has been made to investigate the performance of the Joule–Thomson refrigeration system with the addition of a heat exchanger in between the condenser and the expansion device. In order to study the performance of the system experimentally, a Joule-Thomson refrigeration system experimental setup has been developed with mixture of R290/R600a (40/60, 50/50, 60/40 and 70/30 by weight) are used as environmental friendly refrigerant mixtures and experiments are conducted. The effect of evaporator temperature on the coefficient of performance, exergy efficiency and exergy destruction ratio of the J-T system are investigated. The Joule–Thomson refrigeration system with compact heat exchanger yields higher coefficient of performance by 10.45% and exergy efficiency obtained by 4.25%. Keywords: Coefficient of Performance, Exergy Destruction Ratio, Exergy Efficiency, Heat Exchanger, Joule–Thomson Refrigeration System

The Effect of Evaporator Temperature on Lactic Acid Purity and Recovery by Short Path Evaporation

In this work, the evaluation of lactic acid concentration from a synthetic mixture of water and lactic acid (3 wt% of lactic acid) was carried out using short path evaporation (SPE). The evaporator temperature of a SPE is one of the important technological parameters that determine an evaporator’s operation. In this study, the effect of the evaporator temperature on the lactic acid purity and recovery was observed from 303 to 443 K. The results showed that, in the studied range, the evaporator temperature of 353 K can be regarded as the best, since an increase of 2.15 times in the solution concentration was obtained.

Influence of Evaporation Temperature on the Morphology, Polymorph and Mechanical Properties of Poly(vinylidene fluoride) Solution-Cast Membranes

In this study, PVDF membranes were prepared by solution-cast method. The effects of evaporation temperature on the morphology, polymorph and mechanical properties of such prepared membranes were studied. It was found that perfect spherulites were observed in the solution-cast membranes. FESEM photomicrographs of the membranes showed dense structure. PVDF mainly crystallized into α phase. In the solution-cast process, the spherulite size increased as evaporation temperature was increased from 120 °C to 150 °C, when the evaporation temperature was 165 °C, spherulite size decreased. And the tensile strength increased with the decrease in spherulite size.

Environment Friendly Mixed Refrigerant to Replace R-134a in a VCR System with Exergy Analysis

Study on environment friendly mixed refrigerant to replace R134a in vapour compression refrigeration (VCR) System. The mixed refrigerants investigated are propane (R290), butane (R600), isobutene (R600a) and R134a. Even though the ozone depletion potentials of R134a relative to CFC-11 are very low; the global warming potentials are extremely high and also expensive. For this reason, the production and use of R134a will be terminated in the near future. Hydrocarbons are free from ozone depletion potential and have negligible global warming potential. The results showed that, mixed refrigerant with charge of 80 g satisfy the required freezer air temperature when R134a with a charge of 110 g is used as refrigerant. The actual COP of refrigerator using mixed refrigerant was almost nearer that of the system using R134a as refrigerant. The coefficient of performance of the vapour compression refrigeration system using mixed refrigerant MR-3 [R134a/R290/ R600a/ R600 (20/35/40/5)] is having very close value with R134a and the Global warming potential of MR-3 is negligible when compared with R134a. Hence the mixed refrigerant MR-3 is chosen as an environmental friendly alternate refrigerant to R134a. The exergy analysis of the vapour compression refrigeration system using R134a and all the above mixtures are investigated. The effect of evaporator temperature on exergy efficiency and exergy destruction ratio of the system are experimentally studied. The exergy defect in the compressor, condenser, expansion device and evaporator are also obtained. Key words: R134a, Mixed refrigerant, Chlorofluorocarbons, Propane, Butane, Isobutene, REFPROP, COP, ODP, GWP, Exergy, VCR System.

Exergy analysis of a domestic refrigerator using eco-friendly R290/R600a refrigerant mixture as an alternative to R134a

The aim of the present work is to bring out an exergy analysis of the hydrocarbon refrigerant mixture of R290/R600a as an alternative to R134a on the performance of a domestic refrigerator which is originally designed to work with R134a. The performance of both refrigerants was evaluated using an exergy analysis. The effects of evaporator temperature on the coefficient of performance (COP), exergy loss, exergic efficiency, and efficiency defect in the four major components of the system for R134a and R290/R600a mixture were experimentally investigated. The results obtained showed that the COP of R290/R600a mixture was improved up to 28.5 % than that of R134a. The highest average exergic efficiency of the system (42.1 %) was obtained using R290/R600a mixture at an evaporator temperature of 263 K (−10 °C). The overall efficiency defect in the refrigeration cycle working with R290/R600a mixture was consistently better than R134a.

The determination of performances of polysulfone (PS) ultrafiltration membranes fabricated at different evaporation temperatures for the pretreatment of textile wastewater

The effects of evaporation temperature on properties and filtration performances of polysulfone membrane were investigated with a series of experiments. Membranes were fabricated by phase inversion process at five different evaporation temperatures (25±0.4, 35±0.6, 45±0.5, 55±0.5 and 65±0.6°C). The resulted membranes were characterized by water permeability, MWCO (molecular weight cut-off), AFM, porosity, contact angle and SEM analyses and tested for filtration performances by using a model dye solution (reactive orange 16-RO16) and a real dye-bath textile wastewater. The pore size and density onto the membrane surface become smaller and the surface roughness, porosity, permeability and MWCO values of membranes considerably decreased with the increasing of evaporation temperature. At the pretreatment filtration experiments, the flux values of membranes decreased largely with the increase of the evaporation temperature while the removal efficiencies for color, COD and conductivity parameters increased. At the membrane fouling analysis, the flux reduction ratios (FRR), the filtration (Rt) and fouling (Rf) resistances and the reusable performances of membrane changed directly proportional with roughness, porosity and pore size characteristics of membranes. At the nanofiltration step (NF-270 membrane), the moderate color, chemical oxygen demand (COD) and conductivity removal were showed at permeate of PS-65 membrane (the membrane fabricated at 65±0.6°C).