Ejector Heat Pump Research Articles

Thermodynamic analysis of a parallel type organic Rankine cycle and ejector heat pump combined cycle

A parallel type organic Rankine cycle and ejector heat pump combined cycle with an external heat exchanger is proposed in this paper. The proposed system can recover all the condensing heat for the production of radiant heating water. And the system can adjust the thermoelectric ratio according to the actual needs of users by arranging the expander and the ejector in parallel. Energy analysis and exergy analysis mathematical models of the combined cycle are constructed. The thermal performance of the combined cycle is studied through parameter analysis and exergy analysis. The results show that heat recovery capacity, net power output, and exergy efficiency of the combined cycle are 60.83%, 4.62%, and 30.76% higher than the basic organic Rankine cycle, respectively. The component with the largest exergy destruction is the generator (85.07 kW). Reducing the working fluid ratio can increase the net power output efficiency and exergy efficiency of the combined cycle. And the applicable range of the working fluid flow ratio increases as the evaporating temperature decreases. The combined cycle has advantages in thermal performance and matching comprehensive energy demand.

The equivalent low-dissipation combined cycle system and optimal analyses of a class of thermally driven heat pumps

The performance characteristics, operation, and design strategies of a class of thermally driven heat pumps are investigated due to their important roles in the efficient utilization of low-grade thermal energy. In order to establish a more generic thermodynamic model of thermally driven heat pumps mainly including absorption, adsorption, and ejector heat pumps, low-dissipation assumption is adopted. Accordingly, the associated dissipation parameters accounting for the specific information on the irreversibilities in each heat-transfer process are introduced rather than specifying heat-transfer law. Based on the proposed model, the theoretical results of the coefficient of performance and heat load are derived with regard to two key parameters denoting the size ratio of the two involved subsystems and the matching deviation from reversible limit. The performance characteristics and the optimally operating regions of the whole system are determined and the differences between thermally driven heat pump and refrigerator are highlighted. The proposed model and obtained results further develop the low-dissipation model and may provide a useful description for the operation and design of practical thermally driven heat pumps.

Parametric study and working fluid selection of the parallel type organic Rankine cycle and ejector heat pump combined cycle

To solve the problem of low thermal efficiency and single output form of the basic organic Rankine cycle, a parallel type organic Rankine cycle and ejector heat pump combined cycle is proposed. By deeply utilizing the energy of the low and medium temperature heat source, the system can provide different proportions of power and heating water according to users’ demands. Considering the factors of performance, environmental impacts, flammability, and turning point temperature, five working fluids are selected (i.e., R236ea, R123, R245fa, R365mfc, and R141b). Parametric analysis of the system is performed by constructing the thermodynamic model. Different operating modes of the system are defined according to different heating/power ratios. The results show that each working fluid has its optimal generator temperature to optimize the net power output efficiency. R236ea is more suitable for the system with a net power output efficiency of 6.58% and an exergy efficiency of 42.24%. Compared with the series type combined cycle, the parallel type combined cycle net power output increased by 5.08% and heating capacity increased by 20.71%. This paper can guide the efficient construction of low and medium temperature cogeneration systems.

Thermal and electrical performance assessment of a solar polygeneration system

In this paper, a reliable and cost-effective polygeneration system for an existing test building, able to provide electricity, cooling and heating needs is presented, modelled and assessed. The system relies on solar energy as the primary source (PV and solar thermal collectors). Building cooling demand is achieved with a variable geometry ejector heat pump. To reduce the mismatches between generation and consumption, different types of storage are included (electrical and thermal). A system prototype is under development and will be installed as a demonstration site in Portugal.To assess the test building energy needs, the electricity consumption of all consumers was measured. For the thermal energy demand a numerical model using TRNSYS software was developed. The building thermal performance was validated using experimental data. The numerical model also includes the solar field, thermal energy storage and ejector cycle. To model and simulate yearly electricity production PVSyst software was used.

POLYSOL – Thermal and electrical performance assessment of a cost-effective polygeneration system

Buildings are responsible for a large portion of the energy consumption and harmful emissions to the environment. To change this situation, the European Performance of Buildings Directive requires new buildings to be nearly Zero Energy Buildings. To achieve this goal, energy saving measures combined with large use of renewables on-site must be applied. In this paper, a reliable and cost-effective polygeneration system for an existing test building, able to provide electricity, cooling and heating needs is presented, modelled and assessed. The system relies on solar energy as the primary source (PV and solar thermal collectors). Building heat and cooling demand is achieved with a variable geometry ejector heat pump. To reduce the mismatches between generation and consumption, it includes different types of storage (electrical and thermal). For the test building energy needs assessment, the electricity consumption of all test building consumers was measured. Thermal energy demand evaluation required the development of a dynamic numerical model using TRNSYS software. The building thermal performance was validated using experimental data. The numerical model also includes the solar field, thermal energy storage, ejector cycle subjected to know meteorological conditions and operation control. To model and simulate yearly electricity production PVSyst commercial software was applied. Regarding the thermal energy, it was found that on a yearly basis the energy supplied by the thermal collectors about six times the demand. Nevertheless, on the hourly and daily levels, there are thermal energy shortages, due to the lack of solar radiation or mismatch between production and demand. Regarding the electric energy consumption, the potential electric energy production is about 1.6 times the demand. Like for the thermal energy, on the hourly and daily levels, there are energy deficits mostly in winter, for which an electrical energy storage unit will be used. Additionally, the highest peak occurs in summer because of low solar radiation at the end of the day and high demand due to the high cooling load of the test room.

Simulation of the performance of a gas-fired hot water system with compression-enhanced ejector heat pump using R152a

Natural gas is widely used for space heating because of its low pollutant emissions and high combustion efficiency. Nevertheless, the primary energy efficiency of a gas-fired boiler cannot exceed 100% based on high calorific value. In order to improve the efficiency of natural gas for heating, a gas-fired hot water system with a compression-enhanced ejector heat pump is proposed. The simulation results show that the compressor can sustain the ejector’s high efficiency range while in operation. When the ambient temperature is 0 °C, the primary energy efficiency is substantially higher than that of the conventional ejector heat pump system and gas-fired boiler by 40 and 36%, respectively. When the supply water temperature does not exceed 46 °C, the coefficient of performance and primary energy efficiency of the novel gas-fired hot water system can reach 1.65 and 1.22, respectively.

A theoretical study on a novel combined organic Rankine cycle and ejector heat pump

A novel combined organic Rankine cycle and ejector heat pump is proposed, which combines the organic Rankine cycle and ejector heat pump, and could produce both power output and heat output simultaneously. An ejector is installed on the turbine inlet side to increase the total heat exchange amount of the combined cycle by utilizing the injection capability of the high-pressure primary fluid. Using the heat exchange capacity of the cold source to adjust the matching problem between the primary fluid heat source and secondary fluid heat source. The constant pressure mixing model is used to model the ejector, and a new solution method of the model is proposed. Through the parametric analysis, the results show that the heat exchange of secondary fluid and turbine intake pressure have significant effects on the thermal efficiency and heat recovery capacity. By comparing with the basic organic Rankine cycle, the maximum net power output of the novel combined cycle can be increased by 10.78%, and the maximum heat recovery capacity can be increased by 19.04%.

Performance investigation of a two-phase transcritical CO2 ejector heat pump system

This study of the thermodynamic performance of a transcritical CO2 ejector heat pump cycle presents a numerical analysis under the constraint of constant total heat transfer area. An experimentally validated model of a CO2 heat pump system and a model of a two-phase ejector are combined to perform the study. The effects of chosen parameters on system performance are investigated: operating conditions as determined by the gas cooler and evaporator pressures; ejector design parameters including the primary throat diameter, effective area ratio, and diffuser outlet diameter; system design as defined by the heat transfer area ratio. The results of this analysis allow specifying the optimal range for the design parameters in order to maximize the COP and the heating capacity of the heat pump. The heat transfer area ratio is shown to have important effects on the COP and heating capacity as well as the optimal gas cooler pressure. As the heat transfer area ratio increases, COP and heating capacity increase as well, while the optimum gas cooler pressure decreases. At given ejector geometries and operating conditions, this optimization can increase the COP and heating capacity of the ejector heat pump by approximately 17% and 20% respectively by increasing the heat transfer area ratio.

Characteristics of R718 refrigeration/heat pump systems with two-phase ejectors

The paper describes investigations of R718 refrigeration cycles with two-phase ejector as a compression device. The complex thermal and flow phenomena inside two-phase ejector flow field are analyzed and characteristics of two-phase ejectors are estimated. Results of investigations of numerous refrigeration systems with two-phase ejectors are analyzed and recommendations for optimal geometric parameters of two-phase ejectors are summarized. Novel R718 refrigeration/heat pump systems are proposed: simple two-phase ejector cooling cycle, two-phase ejector heat pump cycle applied in evaporators–concentrators, and combined compact R718 centrifugal compressor–two-phase ejector water chiller for air conditioning application, and their thermal and performance characteristics are estimated.

Reducing of thermal power energy-intensive pro-cesses costs in the mixed fodders technology

Methodological approach to the creation of energy-efficient processes with direct involvement in the produc-tion process of heat pump technology for the preparation of of energy resources in obtaining of mixed fodders of the given particle size distribution was formed. Completed experimental and analytical studies paved the way for the development of energy efficient technolo-gies of mixed fodders with a vapor compression connection (VCHP) and steam ejector (SEHP) heat pumps on the closed thermody-namic schemes. It was shown that the strategy of the operational management of process parameters in the allowable technological properties of the resulting mixed fodder production does not allow a compromise between the conflicting technical and economic param-eters and let the main technical contradiction between productivity and power consumption. The control problem becomes much more complicated when there is no practical possibility of a detailed description of thermal processes occurring in the closed thermodynamic recycles based on the phenomenological laws of thermodynamics considering a balance of material and energy flows in the technologi-cal system. There is a need for adaptive control systems based on the extreme characteristics of the controlled object. The adaptation effect is achieved by obtaining information about the processes occurring in the conditions of technological line of mixed fodders pro-duction equalized particle size distribution, which allows to generate a control signal for the extreme value of the objective function. The scheme of automatic optimization ensuring continuous monitoring of the minimum value of the specific heat energy costs is proposed. It provides optimal consumption of the starting loose mixed fodder and rational strain on the line equipment.

Эксергетический анализ технологии получения порошкообразного продукта из фильтрата барды с использованием пароэжекторного теплового насоса

Эксергетический анализ технологии получения порошкообразного продукта из фильтрата барды с использованием пароэжекторного теплового насоса

Design and Thermodynamic Analysis of a Steam Ejector Refrigeration/Heat Pump System for Naval Surface Ship Applications

Naval surface ships should use thermally driven heating and cooling technologies to continue the Navy’s leadership role in protecting the marine environment. Steam ejector refrigeration (SER) or steam ejector heat pump (SEHP) systems are thermally driven heating and cooling technologies and seem to be a promising technology to reduce emissions for heating and cooling on board naval surface ships. In this study, design and thermodynamic analysis of a seawater cooled SER and SEHP as an HVAC system for a naval surface ship application are presented and compared with those of a current typical naval ship system case, an H2O-LiBr absorption heat pump and a vapour-compression heat pump. The off-design study estimated the coefficient of performances (COPs) were 0.29–0.11 for the cooling mode and 1.29–1.11 for the heating mode, depending on the pressure of the exhaust gas boiler at off-design conditions. In the system operating at the exhaust gas boiler pressure of 0.2 MPa, the optimum area ratio obtained was 23.30.

Three-dimensional CFD modeling and simulation on the performance of steam ejector heat pump for dryer section of the paper machine

A three-dimensional model of the steam ejector heat pump for the dryer section of the paper machine was developed by applying the Computational Fluid Dynamics (CFD) technique, which provided the pressure and velocity distributions of fluid flow in heat pump. The results indicated that the fluid velocity field in heat pump has an incomplete axially symmetrical distribution. The entrainment ratio of the heat pump initially increases rapidly with the increase of the ejected steam inlet pressure and then decreases after the inlet pressure exceeds one certain value. There exists a critical value for the mixed fluid pressure under the given operating conditions. The optimal ratio of the diameter of constant area mixing section to the steam nozzle throat diameter is about 3.4 and the optimal ratio of length to diameter of constant area mixing section L/Dm is 6. An optimal divergence angle of diffuser was observed under different diffuser length. There is an optimized steam nozzle position under the given operating condition where the maximum of entrainment ratio was observed. The CFD technique is found to be an efficient alternative to predict the ejector performance and the conclusions of the research can provide a beneficial reference for structural optimization design of ejector.

Comparative study of indirect photovoltaic thermal solar-assisted heat pump systems for industrial applications

In this paper, a comparative study of indirect photovoltaic thermal solar-assisted heat pump systems for water heating in industry is presented. The solutions to achieve a system with a steam ejector heat pump and a system with a mechanical compression heat pump integrated in a paper mill are proposed. The mathematical models are developed and used to evaluate the performance of these systems for the Bacau, Romania climatic conditions. A numerical study highlights the energy, exergy and economic efficiency of each system for the different operating hot water temperatures supplied. The obtained results show that an increase in the hot water temperature leads to a decrease in the energy, exergy and economic performance and that in an industrial company with continuous operation, the best solution is a photovoltaic thermal system with a steam ejector heat pump.

A new ejector heat exchanger based on an ejector heat pump and a water-to-water heat exchanger

As urban construction has been developing rapidly in China, urban heating load has been increasing continually. Heating capacity of the existed primary heating network (PHN) cannot meet district heating requirements of most metropolises in northern China. A new type of ejector heat exchanger (EHE) based on an ejector heat pump and a water-to-water heat exchanger (WWHE) was presented to increase the heating capacity of the existed PHN, and the EHE was also analyzed in terms of laws of thermodynamics. A new parameter, the exergy distribution ratio (EDR), is introduced, which is adopted to analyze regulation characteristics of the EHE. We find that the EHE shows better performance when EDR ranges from 44% to 63%. EHE can decrease the temperature of return water in the PHN to 35°C, therefore, this can increase the heating capacity of existed PHN by about 43%. The return water with lower temperature in the PHN could recover more low-grade waste heat in industrial systems. Because of its smaller volume and lower investment, EHEs could be applied more appropriately in district heating systems for long-distance heating and waste heat district heating systems.

Study on Application of Steam Ejector Heat Pump in Partial Innovation of Power Plant Thermal Regenerative System

The exhaust steam heat of steam driven feed pump small steam turbine is considerable in modern coal-fired power generating unit, most of which is adopted the way of wet cooling through the condenser as same as main steam turbine for condensing steam turbine unit, all the waste heat with it is taken away by circulating cooling water and not used effectively. This paper will propose the way of part of exhausted steam of small steam turbine recycled to the regenerative extraction steam system to heat condensate based on steam ejector heat pump, so as to use the exhausted steam effectively and analyze the thermal economic index of different schemes by using equivalent enthalpy drop method. The results show that it produces best economic benefits when exit steam of steam ejector heat pump is recycled to steam extraction of the fourth section.

Study of an innovative ejector heat pump-boosted district heating system

An Ejector heat pump-boosted District Heating (EDH) system is proposed to improve the heating capacity of existing district heating systems with Combined Heat and Power (CHP). In the EDH, two ejector heat pumps are installed: a primary heat pump (HP1) at the heating station and a secondary heat pump (HP2) at the heating substation. With the EDH, the low-grade waste heat from circulating cooling water in the CHP is recycled and the temperature difference between the water supply and the return of the primary heating network is increased. A thermodynamic model was provided. An experimental study was carried out for both HP1 and HP2 to verify the predicting performance. The results show that the COP of HP1 can reach 1.5–1.9, and the return water temperature of the primary heating network could be decreased to 35 °C with HP2. A typical case study for the EDH was analyzed.

Exergetic and sustainability performance assessment of geothermal (ground source) ejector heat pumps

Although ejectors have been used in cooling/refrigeration and Heat Pumps (HP) applications for a long time, utilisation of Geothermal Ejector Heat Pump (GEHP) with Ground–Heat Exchanger (GHE) is a new idea, which has recently appeared in the literature. In this study, we model a GEHP system with a GHE in terms of exergetic aspects and apply our model to this system in the heating mode. The system consists of mainly three parts, namely a GEHP unit, a GHE, and a heat distribution system. We determine the exergy transports between the components and the consumptions in each of the components of the whole system and we also calculate exergy efficiency and Sustainability Index (SI) values for the system components to evaluate its performance. In this regard, exergy efficiency values for the GEHP unit and whole system are calculated to be 85.3% and 84.6% on the product/fuel basis at dead (reference) state values for 19°C and 101.325 kPa, respectively. An improvement of about 16.17% in the energetic and exergetic coefficient of performance value of the GEHP unit is obtained by adding an ejector to the HP system. SI values for some system components such as ejector, compressor, condenser and evaporator are also obtained to be 1.82, 2.79, 3.22 and 3.94, respectively.

Thermoeconomic analysis of a low-temperature multi-effect thermal desalination system coupled with an absorption heat pump

This study presents a thermal and economic performance analysis of a LT-MEE (low-temperature multi-effect evaporation) water desalination system coupled with an LiBr–H 2O ABHP (absorption heat pump). A 60–78% water production increase over a stand-alone LT-MEE run at the same heat source conditions can be obtained owing to the coupling. A detailed thermodynamic sensitivity analysis of the ABHP-MEE is performed. Although ABHP is usually considered to be more efficient than an EHP (ejector heat pump), we also compare the thermal performance of the ABHP-MEE with an integrated EHP-MEE system. The results show that the ABHP has a more favorable thermal performance than the EHP only in certain parameters ranges. The reasons and these parameters ranges are discussed. The economic analysis of the ABHP-MEE shows that the capital cost of the ABHP accounts for a very small part of the water cost, and when designing an ABHP for an existing MEE unit, the parameters selection of an ABHP for lower water cost is consistent with that for better thermal performance. The unit steam cost is an important factor in determining whether the ABHP-MEE or the EHP-MEE is economically favorable, with the influence discussed. Also, a recommended general procedure for economic comparison between ABHP-MEE and EHP-MEE is outlined.

Vertical ground coupled steam ejector heat pump; thermal-economic modeling and optimization

A vertical ground coupled steam ejector heat pump is a Ground Coupled Heat Pump (GCHP) with closed Vertical Ground Heat eXchanger (VGHX) which utilizes the steam ejector type of refrigeration cycle instead of the vapor-compression type. This paper presents the modeling and optimizing a Ground-Coupled Steam Ejector Heat Pump (GC-SEHP) with closed VGHX. The system included two main sections of VGHX and steam ejector heat pump (SEHP), and was optimized by minimizing its total annual cost (TAC) as the objective function. Two optimization techniques (Nelder–Mead and Genetic Algorithm) were applied to guarantee the validity of optimization results. For the given heating/cooling loads as well as for various climatic conditions, the optimum design parameters of GC-SEHP with closed VGHX were predicted. Furthermore, the changes in TAC and optimum design parameters with the climatic conditions, cooling/heating capacity, soil type, and number of boreholes were discussed.