Condenser Outlet Research Articles

Energy and exergy analysis of a Linde-Hampson refrigeration system using R170, R41 and R1132a as low-GWP refrigerant blend components to replace R23

This study presents a comprehensive comparative analysis of the thermodynamic performance of a single-stage Linde-Hampson refrigerator (LHR) for refrigerant couples, namely R1234yf + R170, R1234yf + R23, R1234yf + R41 and R1234yf + R1132a, to seek the most suitable substitute for R23 at the temperatures down to −60 °C. The compressor input power, cooling capacity, coefficient of performance, exergy loss and exergy efficiency are selected as the objective functions. The operating parameters include the evaporation temperature, suction pressure, and condenser outlet temperature. The compositions of each binary mixture were obtained from the vapor-liquid equilibrium behavior according to the suction pressure and target evaporation temperature. Simulation and comparative study show that better energy and exergy performance are obtained with all the replacements under all studied conditions compared to R23. Further results show that the R1234yf + R41 mixture performs better, and hence is suggested as the most promising alternative couple for the single-stage LHR at −60 °C. By properly increasing the suction pressure and decreasing the condensation temperature, the system performance can be enhanced. This indicates that a multi-objective scheme has the potential to significantly improve the performance of low-temperature applications.

Feasibility study and in-depth performance assessment of needle valve using as expansion device in refrigeration system

The needle valve (NEV) has high potential for further using as the automatic expansion device in the refrigeration system. However, the experimental proof is required for further developing the automatic controller for operation. This paper proposes the feasibility study and performance map of the needle valve (NEV) using as the expansion device in a small vapour compression refrigerator (VCR). The relevant parameters produced by NEV are compared with those using capillary tube (CT) and thermostatic expansion valve (TEV) which are the conventional device. The system COP, superheated degree at evaporator outlet (SHDevap-out), subcooled degree at condenser outlet (SCDcon-out), mass flow rate, volumetric refrigeation capacity, compressor's specific work and refrigerant quality are considered for comparisons. Additionally, the economic assessment of using NEV compared with the other two devices is proposed. It is found that COP produced by NEV are similar to TEV which is better than CT. The ecomnomic assessment indicates that the NEV produces similar useful cooling energy per unit cost to that using TEV which is higher than CT. Overall results indicate that the NEV can efficiently be used as the expansion device in VCR which is alternative to the conventional expansion devices.

Comparative environmental impacts and emission reductions of introducing the novel organic Rankine & Kalina cycles to recover waste heat for a roller kiln

Abstract In order to simultaneously utilize the flue gas and cooling gas of a roller kiln, the novel organic Rankine (ORC) & Kalina cycles (KC) with parallel double-evaporator (PD) including PD-BORC, PD-RORC, PD-KC11 and PD-KC34 are introduced for the waste heat recovery. To evaluate the environmental influences performance for the recommended thermodynamic cycles, environment impact loads and emission reductions analysis are employed from the life-cycle perspective. Also, to select a more environmentally friendly model, the system environmental influences based on thermodynamic, economic, environmental and watery criteria are investigated. Results show that under the four criteria, the pump contribute mostly to GWP (global warming potential), AP (acidification potential), EP (eutrophication potential) and HTP (human toxicity potential), evaporation unit is dominant in POCP (photochemical ozone creation potential) and SWP (solid waste potential), and both evaporation unit and pump have the main influence on SAP (soot and dust potential). Meanwhile, operation phase makes the greatest contribution to GWP, AP and HTP, construction phase has the greatest influence on POCP and SWP, and construction and operation phases account for the largest proportion of EP and SAP. It can also be concluded that SAP has the most serious impact on the environment while POCP is the least significant factor. Besides, from the perspective of environment impact load, PD-BORC is the best selection, and the system design based on environmental criterion has the minimum value. Also, in terms of the emission reduction, PD-KC34 is the priority selection, and the maximum emission reduction can be achieved under thermodynamic criterion. Furthermore, the reduction ratio of environment impact load can be increased with increasing the evaporator inlet temperature, decreasing the condenser outlet temperature, increasing the superheat degree (PD-ORCs) and decreasing the superheat degree (PD-KCs), and decreasing the ammonia concentration (PD-KCs).

Experimental investigation of a heat-source tower heat pump with self-regenerator using subcooling heat

The heat-source tower heat pump, a frost-free heat pump with superior energy efficiency, has been used for heating in cold regions. Because the solution in the heat-source tower absorbs moisture continuously from the outdoor air and becomes diluted during heating, solution regeneration is necessary. However, existing regeneration technologies have various disadvantages, such as a reduced heating capacity, decreased system efficiency, or the need for additional equipment. Hence, it is urgent to develop a regeneration technology with low cost, high energy efficiency and little impact on heating capacity. In this study, a heat-source tower heat pump with a self-regenerator is proposed and experimentally investigated. To regenerate the weak solution in the tower, the system uses the subcooling heat of the refrigerant at the condenser outlet as a heat source. The operating characteristics of the system in three heating modes are investigated experimentally. The results indicate that in the heating mode with self-regeneration, the heating capacity of the system is similar to that in the heating mode without regeneration under the same operating conditions. The system realizes efficient regeneration and can operate continuously, although the system efficiency is 2.5–5.1% lower than that of a system without regeneration. In addition, the regeneration efficiency of the proposed system reaches 3.13–11.98 under the condition where the regeneration temperature ranges from 18 to 45 °C. These results demonstrate that the proposed system can be used in cold regions.

Performance parameters analysis of an organic Rankine cycle for power generation from the heat of cooling scramjet

An organic Rankine cycle (ORC) for power generation system is proposed for cooling scramjet. The heat which must be taken away by fuel coolant from cooling scramjet is converted to other forms of energy to decrease fuel coolant flow. A parametric study of an ORC power generation system has been performed. The multiplication ratio of fuel heat sink, the efficiency and output power of the system changing with the condenser outlet fuel coolant temperature are evaluated. The results show that the optimal condenser outlet fuel coolant temperature is 510K in a certain working condition, and the multiplication ratio of fuel heat sink is 0.0635, the efficiency of the system is 11.74% and the output power is 35.13kW. The effect of the cycle pressure ratio on the efficiency, output power and the multiplication ratio of fuel heat sink is also analyzed and it has a big significant influence. It is known through thermodynamic analyses that ORC power generation system for cooling scramjet would reduce the fuel coolant flow and give some output power for hypersonic vehicle.

Exergy and Energy Analyses of Dual-Temperature Evaporator Split AC System Incorporated A Capillary Tube and A Two-Phase Ejector

This study was aimed to investigate performance of a split type air conditioning (SAC) system applying exergy destruction method. A numerical model was established based on exergy destruction analysis of a Condenser Outlet Split-Split Air Conditioning (COS-SAC) system integrated with dual-temperature evaporator and incorporated capillary tube and ejector as expansion devices. An experimental test system was also established to experimentally validate the model. Two type of refrigerants R-290 and R-22 were involved in the evaluations. The Coefficient of Performance (COP) of the ejector COS-SAC system, exergy destruction, and exergy efficiency were determined and compared with those in the SAC system utilizing capillary tube. The results showed there was a significant improvement in the overall exergy efficiency of the COS-SAC systems. The COP of the COS-SAC system was also found to be better than the COP of the SAC system.

A machine learning approach for modeling and optimization of a CO2 post-combustion capture unit

Reducing CO2 emissions from fossil fuel fired power plants has been a major environmental concern over the last decade. Amongst various carbon capture and storage (CCS) technologies, the utilization of solvent-based post-combustion capture (PCC), played a major role in the reduction of CO2 emissions. This paper illustrates the development of machine learning models to predict the outputs of the PCC unit. A fine tree, Matérn Gaussian process regression (GPR), rational quadratic GPR, and squared exponential GPR models were developed and compared with a feed-forward artificial neural network (ANN) model. An accuracy of up to 98% in predicting the process outputs was achieved. Furthermore, the models were utilized to determine the optimum operating conditions for the process using a sequential quadratic programming algorithm (SQP) and genetic algorithm (GA). The use of the machine learning models has proven to be very useful since the complete mechanistic model is too large, and its runtime is too long to allow for rigorous optimal solutions. The machine learning models and optimization problems were developed and solved using MATLAB. The data used in this work was obtained from simulating the process using gPROMS process builder. The inputs of the model were selected to be reboiler duty, condenser duty, reboiler pressure, flow rate, temperature, and the pressure of the flue gas. The models were able to accurately predict the outputs of the process which are the system energy requirements (SER), capture rate (CR), and the purity of condenser outlet stream (PU).

Experimental validation of an advanced heat pump system with high-efficiency centrifugal compressor

In order to achieve a COP of compression heat pumps greater than 6 with the temperature lift of at least 30 °C, a two-cycle parallel connected heat pump system is proposed in this paper. The theoretical simulation of the two-cycle parallel heat pump system is performed and the system performances under different condenser outlet water temperature are assessed. A heat pump prototype using the two-cycle parallel system with a heating capacity of 9000 kW is developed and an experimental study on the system performance is conducted. The results show that the COP of the two-cycle parallel system is 6.93 when the evaporator inlet/outlet water temperature is 30/25 °C and the condenser outlet water temperature is 60 °C. As the condenser outlet water increases from 60 °C to 68 °C, the heating capacity decreases by 6.8% and the power consumption increases by 11.6%. The two-cycle parallel heat pump system is able to lower the condensing pressure and power consumption, resulting in the improvement of the system COP. All the results indicate that the heat pump using two-cycle parallel system with gradual water heating has a good prospect in industrial heating applications for its high efficiency and great capacity.

Effects of Nozzle Exit Position on Condenser Outlet Split Ejector-Based R600a Household Refrigeration Cycle

The objective of this study is to investigate the performance characteristics of a small-sized R600a household refrigeration system that adopts a condenser outlet split (COS) ejector cycle under various operating and ejector geometry conditions. The coefficient of performance and pressure lifting ratio of the COS ejector cycle were analyzed and measured by varying the entrainment ratio, compressor speed, and nozzle exit position. The optimum nozzle exit position in the COS ejector cycle adopted to achieve the maximum cycle performance was proposed as a function of the compressor speed and entrainment ratio. The optimum nozzle exit position was 0 mm when the entrainment ratio and compressor speed were low, and it increased as the entrainment ratio and compressor speed increased owing to the associated internal pressure drop in the suction section.

A pseudo two-phase model to study effects of non-condensable gases on the water autonomy of a direct methanol fuel cell system

In a direct methanol fuel cell (DMFC) system, water at the condenser outlet is recirculated into the mixing chamber where it mixes with pure methanol and anode outlet stream. The selection of condenser design and operating conditions plays a key role in the successful operation of the system with water autonomy. In this study, a novel pseudo two-phase computational fluid dynamics (CFD) model is proposed to investigate the condensation capability of the condenser under the operating conditions of a DMFC system. The condenser model is simplified by implementing an iterative multi-domain approach where continuity at the decoupled domain interfaces is satisfied by the convergence of boundary conditions. The proposed thermofluids model is validated with experimental data. Through the model, the performance of the condenser is investigated for DMFC operating conditions. The results show that the amount of non-condensable gases, the velocity and the saturation level of cathode exhaust gas (CEG) are the key parameters in these scenarios. The highest condensation effectiveness is calculated for the saturated CEG flow scenario with lower velocity and lower content of non-condensable gases, while the lowest condensation effectiveness is calculated as for the under saturated CEG flow scenario. Another important result is that the increment of the amount of the non-condensable gases throughout the downstream distance is found as 4% which results in the decrement of the saturation and film temperature by 8 K and 4 K, respectively. In addition, it is found that when the inlet velocity of CEG decreases from 0.82 m•s-1 to 0.18 m•s-1, the overall condensation rate decreases by 55%.

An experimental investigation on the coefficient of performance of the small hot water heat pump using refrigeration R410A and R32

Hot water is an important factor in domestic life and industrial development. Today, the heat pump is used to produce hot water more and more popular because it has many advantages of saving energy compared to the method of producing hot water by the hot water electric heater. The main aim of this study is to evaluate of the coefficient of performance (COP) of the small hot water heat pump using refrigeration R410A and R32. The capacity of both hot water heat pump is similar, one using new refrigerant R32 and other using refrigerant R410A. These heat pumps were designed and installed at the Ho Chi Minh City University of Technology and Education to evaluate the COP for the purpose of application the new refrigerant R32 for hot water heat pump. The compressor capacity is 1 Hp, the volume of hot water storage tank is of 100 liters and is insulated with thickness of 30 mm to reduce the heat loss to invironment, the required hot water temperature at the outlet of condenser is 50 oC, and the amount of required hot water is 75 liters per batch and is controlled by float valve. The experimental results indicate that the COP of the heat pump using the new refrigerant R32 is higher than heat pump using refrigerant R410A from 9% to 15% when the experimental conditions such as ambient temperature, initial water flow rate through the condenser and the required temperature of hot water were the same. In addition, the effect of the ambient temperature, initial water temperature and water flow rate were also evaluated.

Experimental investigation of the influence of thermoelectric subcooler on the performance of R134a refrigeration systems

This paper presents an experimental study about the influence of a thermoelectric subcooler (TESC) on the performance of a refrigeration system that uses R134a as its working fluid. In this study, a TESC device was designed, fabricated, and attached to a condenser outlet tube. The refrigeration system’s cooling capacity, coefficient of performance (COP), and total power consumption resulting from its integration with the TESC were investigated. Degrees of subcooling within a range of 0–8 K were taken into consideration. The results indicated that the cooling capacity necessary for subcooling, which was provided by the TESC device, increased, but the COP of the TESC (COPTESC) decreased. The results also showed that the R134a refrigeration system benefitted from the TESC when the degree of subcooling increased. Using the TESC device increased the overall system COP by 27.31% and increased its cooling capacity by 50.72% at 8 K, which was the maximum degree of subcooling studied. Without taking the TESC device’s power consumption into account, the overall system COP improved by 50.72%.

The effects of the parameters of a refrigeration system working with R600a on the non-equilibrium subcooled two-phase flow of the refrigerant

Abstract Household refrigerators built with vapor compression refrigeration systems use capillary tubes as expansion devices because of their low cost and simple structure. To prevent decreasing mass flow of the refrigerant and ensure the stability of the system, the refrigeration system is designed so that the refrigerant enters the capillary tube in a subcooled liquid state rather than a saturated two-phase state. However, previous researchers have reported that a two-phase flow entered the capillary in a refrigeration system running with R600a even though the refrigerant was under the subcooled temperature condition. The observed two-phase flow was in a thermodynamic non-equilibrium state, which is a mixture of subcooled liquid and subcooled vapor. Experiments were performed to investigate the effects of the refrigeration system's operating conditions on the contents of the non-equilibrium vapor phase of R600a. Experimental results demonstrated that the void fraction was changed by the system parameters in addition to the pressure and temperature. The void fraction of the non-equilibrium R600a two-phase mixture at the condenser outlet was reduced with increases in degree of subcooling, refrigerant mass flow rate, flow resistance of capillary tube, and decrease in thermal resistance on the secondary side of the condenser. The parameter that caused the biggest change in void fraction was the flow resistance of capillary tube (which was changed by a metering valve in front of capillary tube) while the effects of changes in pressure and refrigerant charge were small.

Aluminum compound forms in the Al–H2O system as applied to operating conditions of Dry Cooling Towers

One of important indicators of reliable operation of the steam-water cycle at power plants is water chemistry. Special chemicals are used to adjust properties of working fluids. At designing a new unit the chemicals are selected on the basis of parameters of water, steam and materials, used in different parts of the cycle.Another indicator is minimizing the cooling water loss. Typical loss of cooling water is about 5% of total water amount. This loss is associated with evaporation, droplet carry-over, and blowdown in cooling towers.For power plants, it is typically recommended to use dry cooling towers for minimizing the cooling water loss. In dry cooling systems, cooling water with low amount of impurities goes to mixing condenser, where turbine steam condensation occurs. Then one portion of mixed water flow at the condenser outlet is supplied to the boiler or steam generator feed water loop. Another portion is returned back to the cooling tower. Inside the cooling tower, water is cooled down by passing through air-cooled heat exchangers manufactured of aluminium or steel alloys.On the basis of Pourbaix diagram it is proposed to evaluate the influence of water chemistry on the forms of existence of aluminium compounds in dry cooling towers. The results of calculations are compared with the experimental data.

Dynamic Operational Characteristics for Condenser and Correlative Equipment

Effective control of condenser backpressure and outlet supercooling plays important role in thermal deaeration process. The back pressure model of condenser is established to analyze the influence of condenser pressure and temperature on circulating water flow, circulating water temperature and suction capacity of air ejector. The dynamic control characteristics and ability of the above factors to backpressure are analyzed.

Steady-state Operational Characteristics for Condenser and Correlative Equipment

Effective control of condenser backpressure and outlet supercooling plays important role in thermal deaeration process. The backpressure model of condenser is established to analyse the pressure and temperature impact of circulating water flow, circulating water temperature and suction capacity of air ejector. The steady-state control characteristics and ability of the above factors to backpressure are analyzed.

Development of Flue Gas Desulphurization Reactor for Reducing SOX Emission from Flue Gases Emitted in Thermal Power Plants

Electrical energy produced in any country is one of the development measures takes place in that country. The energy produced is mainly based on the available resources such as flowing water, coal, oil, gas, nuclear fuels, wind, solar etc. The accessibility of bounty coal in India had provoked the power plant organizers to introduce coal based warm power stations. During the pre-autonomy and post-freedom period in mid fifties, the need was to create control and subsequently much consideration was not paid to the contamination angle and this proceeded up to late seventies. The awareness made by contamination impact on the general public and the colossal measure of disintegration exposed to the gear constrained the specialists to make contamination standards increasingly stringent. These convincing standards which appeared in eighties required the power plant faculty to change the contamination control gear in the current power plants introduced during early days. Most of intensity plants in India going from not many MW to 500 MW or more are of pounded fuel terminated boilers using low calorific, low coal sulfur, high debris content sub-bituminous coal. Due to burning of the coal, emissions such as Particulate Matter (PM), Oxides of Sulphur (SOx) and Oxides of Nitrogen (NOx) apart from CO2, CO are carried away to the atmosphere through the flue gas. In this paper, the methodology to reduce SOx from flue gas in a coastal power station in is discussed and the optimum methodology adopted is Seawater Flue Gas Desulphurisation (SWFGD) using the alkalinity of the seawater to scrub SO2 from the flue gas. The seawater used in the FGD system is from the once through Condenser outlet of the Turbine system and since there is no by-product to be disposed, the seawater FGD is the optimum SOx reducing mechanism for a coastal thermal power station.

Performance assessment of an ejector enhanced dual temperature refrigeration cycle for domestic refrigerator application

Recently, more than 10% energy saving potential was experimentally demonstrated in the condenser outlet split ejector expansion refrigeration cycle when compared with a conventional refrigerator. Nevertheless, introducing two-phase refrigerant into the evaporator causes excessive pressure drop, and compression of redundant vapor counteracts the ejector performance. To overcome these challenges, a modified cycle is proposed by adding a separator to minimize vapor feeding into the low-temperature evaporator. A cycle model is developed and verified by experimental data achieving 10% accuracy. Theoretical investigations of the new cycle indicate 7.7% and 5.5% efficiency and volumetric cooling capacity improvement comparing with the conventional condenser outlet split cycle at nominal conditions. Impacts of evaporating temperature, condensing temperature, pressure drop of the evaporator, heat recovery effectiveness, and separator efficiency are discussed. This study offers an option to further improve energy efficiency for the dual temperature domestic refrigerator.

Experimental study on thermal performance of a loop heat pipe with a bypass line

The loop heat pipe with both flat evaporator and boiling pool (NLHP) has much higher maximum heat flux than conventional loop heat pipe (LHP). However, the serious temperature overshoot and the startup time difference between the evaporator and boiling pool have become a bottleneck of the NLHP. In this study, a loop heat pipe with a bypass line (BLHP) is proposed to improve the startup characteristics of the NLHP. The effects of the bypass line, time difference, boiling pool heat load and evaporator heat load on the thermal performance of the BLHP are experimentally investigated. The results indicate that the bypass line, which is installed between the condenser outlet and the first vapor line, accelerates the return of working fluid and reduces the adverse effect of the heat leakage. The temperature overshoot is virtually eliminated and the BLHP can operate stably at various evaporator and boiling pool heat loads under a broad range of time differences. Furthermore, the BLHP reduces the heating wall temperature by 3.9–8.1 °C and thermal resistance by more than 10% under various heat loads compared with the NLHP. While maintaining the heating wall temperature within 85 °C, the maximum heat flux is 39.3 W·cm−2, which is much higher than most conventional LHPs using methanol as working fluid.

Analysis on full CO2 capture schemes in NG/O2 combustion gas and steam mixture cycle (GSMC)

The nature gas and pure oxygen (NG/O2) combustion gas and steam mixture cycle (GSMC) is a novel power generation cycle using NG/O2 combustion product and circulation H2O as the turbine working medium, which can implement efficient power generation, CO2 capture and energy shifting. In GSMC, cold energy of liquefied natural gas (LNG) and liquefied oxygen (LO2) is used for CO2 capture. The CO2 capture schemes are analyzed to improve the CO2 capture as well as the system efficiency. The main means to increase the CO2 capture and extend CO2 full capture range include the reduction of CO2 liquefaction enthalpy drop and the conservation of cooling energy consumption in CO2/moisture separation. Lower efficiency is always a penalty of the full CO2 capture especially with higher condenser outlet temperature. The optimal scheme is different under different conditions such as parameters of turbine inlet, cooling water, and CO2 liquefaction. At turbine inlet of 30MPa/1000 °C and condenser outlet of 18kPa/38 °C, the efficiency drop is 1.18% for the full CO2 capture of the improved scheme, while the CO2 capture ratio of the original GSMC scheme is less than 60%. The distinctive CO2 capture of GSMC is summarized as system indispensable, scheme optional and method promotable.