Heat Pump Equipment Research Articles

Performance characteristics of a heat pump using renewable transcritical CO2 refrigerant for heating water

ABSTRACT Among non-toxic and inflammable working fluids, carbon dioxide (CO2) proving a possible choice of refrigerant is gaining full status because of its reducing capacity of global warming and ozone depletion. Heat pump (HP) equipment uses energy more rationally to heat water by reducing emissions and global warming caused by conventional refrigerants. HP capability demands an environmentally friendly refrigerant for their full utilization and high energy saving as well to attaining higher coefficient of performance (COP) without much design corrections. CO2 is checked for sustainability to eliminate the standardized refrigerants such as chlorofluorocarbons (CFC) and hydro-CFC. In this work, the performance of CO2 as an alternate refrigerant in HP for heating water at different pressure, flow rates, evaporator fan speed and preheating have been investigated. HP is accommodated with two condensers. The results showed that the increased mass flow rate had increased COP, overall heat transfer (HT) coefficient (U) and HT. However, logarithmic mean temperature difference was decreased for increasing evaporator’s fan speed and pressure. The outlet water temperature (TWO) of second condenser increased with decreasing water flow rate. Improved COP, HT and TWO of HP are observed from the experimental evaluation in case of preheating of water.

Оцінка ефективності вироблення теплової енергії теплонасосними станціями на основі теплоти низькотемпературних підземних вод за методологією повних енергетичних витрат

Heat pump station (HPS) as a source of heat supply for district heating system is considered as an alternative to heating boilers on fossil fuels (mainly on natural gas). One of the promising areas of application of powerful HPS, which currently is being studied actively, is their use as consumers-regulators in the control of electrical load in power systems. In this article, we consider groundwater (deep-well water), which lies at a shallow depth and has stable parameters throughout a year, as a source of low-potential heat. On the territory of Ukraine, there are regions with sufficient groundwater reserves that can be used as a source of low-potential heat for HPS. We carried out calculation of the energy consumption for construction, operation and liquidation of HPS on the example of HPS project with an installed heat capacity of 9 MW, consisting of 3 heat pumps with a capacity of 1.9 MW each and a peak gas boiler with a capacity of 3.2 MW, with regard for a typical schedule of heat loads under conditions of Kyiv. The efficiency of such HPS was determined by the method of estimating the total energy costs by comparing the obtained characteristics with similar characteristics of a gas boiler house of the same capacity. We determined energy consumption for the creation of all elements of HPS and its construction: heat pump and other equipment, station building, drilling and arrangement of wells, pipelines, and peak gas boiler. Energy consumption for the creation and operation of an autonomous gas boiler house of the same capacity was calculated. The reduction of energy consumption for the creation of HPS due to the use of polyethylene-propylene pipes instead of steel is determined. The comparison of energy consumption shows that the creation and operation of HPS on deep-well water with a peak boiler house during the first year of operation compensates the energy consumption for its creation and ensures further energy saving. Operation of such HPS with the use of deep-well water will provide an almost fourfold energy saving as compared with an autonomous boiler house. Keywords: energy consumption, comparative analysis, heat pump systems, groundwater, deep-well water, autonomous boiler house, heat supply

EFFICIENCY OF HEAT PUMP AND ADSORPTION SYSTEM OF CONSERVATION OF ENERGY EQUIPMENT

The paper presents the development of heat pump and adsorption system conservation metal equipment. This system is intended for air drying which is used for long-term conservation of power equipment on the plant station. The processes corrosion of metal details are slowed down when the relative humidity is less than 40%, so this system is designed to provide deep air dehumidification at low electricity costs. A theoretical model of this system is developed in the article and presented calculation of this system. A mathematical model for numerical study of the system operation is developed. The numerical analysis of thermodynamic efficiency was performed, the change of the air mixture parameters at the main points of the system was investigated, the influence of the change of temperature and the relative humidity of the surrounding air on the system operation was analyzed and shows some conclusions. The limits of real-world usage of this system are also analyzed and presented where can be used this system and her benefits. The results obtained show that the application of this system allows to significantly reduce the specific consumption of electric energy for drying the working air compared to the base system without the use of a heat pump for any values of the ambient air parameters. This conclusion presented that use heat pump decrease energy consumption without deterioration of the process of air dehumidification. The graphical dependences of the system performance on a wide range of operating temperatures and humidity of the outside air were obtained. Also, graphical dependences of the heat pump energy conversion factor and air parameters at the main points of the system over a wide range of operating air parameters are presented and analyzed.

Using Tunnel Air Heat in the Heat and Cold Supply Systems of Subway Facilities

An imbalance of thermal operating conditions in a subway has a negative effect on the microclimate in tunnels and stations and eventually leads to accumulation of “thermal pollution” of the soil strata surrounding the subway tunnels and facilities. In turn, such “thermal pollution” results in less intense heat removal to the soil and in air overheating in stations. One of the efficient methods for achieving better energy efficiency of the climate systems and for improving the microclimate in the Moscow Subway’s underground facilities is to use heat pump systems with recovery of the tunnel air heat for supplying heat and cold for station complexes. The article presents the main results obtained from experimental investigations of the thermal operating conditions at some stations of the Moscow Subway. In particular, air temperature in the subway tunnel spaces was measured in the summer and winter seasons. As a result, the main factors influencing the temperature operating conditions in the subway tunnels have been revealed. Based on the results of the experiments, it can be recommended to put heat pumps into operation in the tunnels for setting up a comfortable microclimate in the subway. As an example, the results from testing this process solution are presented through analyzing the efficiency of the heat pump-based heat supply system of the Salar’evo experimental station’s complex. The analysis of the Salar’evo station’s heat pump-based heat supply system has demonstrated its successful operation in the subway along with good compatibility between the subway systems and heat pump unit at the design and operation stages. Application of heat pump equipment in the heat and cold supply systems of subway facilities is not only significantly cheaper than the conventional technology in terms of one-time capital investments but also makes it possible to save more than 80% of energy in the course of operation.

Improving system efficiency for a variable-capacity/variable-blower-speed residential heat-pump system with multizone ductwork

This article describes efficiency improvements resulting from incorporating zonal airflow control into a variable-capacity/variable-fan-speed residential air-conditioning system. The results described are based on full-scale laboratory testing of prototype heat-pump equipment connected to a “typical-design” residential duct system located within a climatic chamber used to produce a range of summer climate conditions. The ductwork and air handler were located in the same space as the condenser (with exhaust venting), and compressor speeds and evaporator airflow rates were manipulated over a range of practical combinations to characterize the efficiency of the entire system. System coefficients of performance (COPs) were calculated based upon the delivery effectiveness of the duct system (cooling ultimately delivered through the grilles, divided by cooling supplied at the evaporator coil) and the efficiency of the HVAC equipment. Our results indicate that duct heat gain can be significantly reduced through an appropriately zoned airflow control mechanism. Zoned ductwork produces the highest system COP at all duct-zone temperatures, with the COP improvements being more pronounced at higher duct-zone temperatures and at lower capacities and airflow rates. Our results also validate the potential for using variable-capacity/variable-fan-speed technology combined with appropriate zonal control demand response events without compromising the efficiency of the air-conditioning system.

Optimal heat pump integration in industrial processes

Among the options for industrial waste heat recovery and reuse which are currently discussed, heat pumping receives far less attention than other technologies (e.g. organic rankine cycles). This, in particular, can be linked to a lack of comprehensive methods for optimal design of industrial heat pump and refrigeration systems, which must take into account technical insights, mathematical principles and state-of-the-art features. Such methods could serve in a twofold manner: (1) in providing a foundation for analysis of heat pump economic and energetic saving potentials in different industries, and further (2) in giving directions for experimentalists and equipment manufacturers to adapt and develop heat pump equipment to better fit the process needs.This work presents a novel heat pump synthesis method embedded in a computational framework to provide a basis for such analysis. The superstructure-based approach is solved in a decomposition solution strategy based on mathematical programming. Heat pump features are incorporated in a comprehensive way while considering technical limitations and providing a set of solutions to allow expert-based decision making at the final stage.Benchmarking is completed by applying the method on a set of literature cases which yields improved-cost solutions between 5% and 30% compared to those reported previously. An extended version of one case is presented considering fluid selection, heat exchanger network (HEN) cost estimations, and technical constraints. The extended case highlights a trade-off between energy efficiency and system complexity expressed in number of compression stages, gas- and sub-cooling. This is especially evident when comparing the solutions with 3 and 5 compression stages causing an increase of the COP from 2.9 to 3.1 at 3% increase in total annualized costs (TAC).

РАЦІОНАЛЬНІ РЕЖИМИ РОБОТИ РЕВЕРСИВНИХ ЧІЛЛЕРІВ З ГРУНТОВИМИ ТЕПЛООБМІННИКАМИ ТА РАДІАТОРНИМИ СИСТЕМАМИ ОПАЛЕННЯ

The rational temperature regimes of the reversible chiller water-water with a ground low-temperature heat exchanger and radiator heating system are revealed. The efficiency of reversing chiller with a soil heat exchanger for different temperatures of the coolant at the outlet of the evaporator is estimated on the basis of technical and economic analysis and using the evaluation method of the life cycle of the product sold in the software product Sima Pro. It is shown that the use of the product life cycle assessment method using ecological indicators for the analysis of the efficiency of heat pump equipment is more promising. The efficiency of the reversible chiller operating in the mode of the heat pump, with the radiator system of heating for different temperatures of the coolant at the outlet of the condenser is analyzed.

Future views on waste heat utilization – Case of data centers in Northern Europe

In this study the potential for data center waste heat utilization was analyzed in the Nordic countries. An overview of upcoming data center projects where waste heat is utilized is presented. Especially in Finland data center operators are planning to reuse waste heat in district heating. However, business models between the district heating network operator and data center operator are often not transparent. The implications of economics and emissions on waste heat utilization in district heating were analyzed through life cycle assessment. Currently the biggest barriers for utilizing waste heat are the low quality of waste heat (e.g. low temperature or unstable source of heat) and high investment costs. A systematic 8-step change process was suggested to ensure success in changing the priority of waste heat utilization in the data center and district heating market. Relevant energy efficiency metrics were introduced to support rational decision-making in the reuse of waste heat. Economic calculations showed that the investment payback time is under the estimated lifetime of the heat pump equipment, when waste heat was utilized in district heating. However, the environmental impact of waste heat utilization depends on the fuel, which waste heat replaces.

E-6 ローエネルギーハウスにおける土壌熱源ヒートポンプ装置の性能試験

E-6 ローエネルギーハウスにおける土壌熱源ヒートポンプ装置の性能試験

Efficiency optimization of a variable-capacity/variable-blower-speed residential heat-pump system with ductwork

The purpose of this study was to evaluate the cooling operation of a variable-capacity/variable-fan-speed residential heat-pump connected to a typical single-zone duct system located outside the conditioned space in a hot-dry climate. This was accomplished through full-scale laboratory testing of prototype heat-pump equipment connected to a complete residential duct system within a climatic chamber wherein a range of summer conditions were simulated. Compressor speeds and evaporator airflows were manipulated over a range of practical combinations to characterize the efficiency of the entire system. The analysis includes the delivery effectiveness of the duct system (cooling delivered to the conditioned space over cooling delivered at the evaporator coil) and the efficiency of the HVAC equipment. Our results indicate that the effectiveness of the distribution system decreases as the compressor and evaporator-fan speeds are reduced, the effect being more pronounced at hotter duct-zone temperatures. Although the ducts perform more efficiently at higher evaporator fan speeds for a given compressor speed, the blower power usage increases, resulting in an optimum cooling Coefficient of Performance (COP) of the overall system at 80% airflow for the different equipment capacities tested. Finally, the delivery effectiveness at individual grilles of the duct system vary disproportionately as the compressor and fan speeds are changed, depending on the dimension and length of the ducts.

수직 밀폐형 심부지열 순환 시뮬레이터의 성능 평가에 관한 연구

While greenhouses have been utilized as a sustainable alternative to traditional soil farming, they are often powered by diesel boilers that necessitate vast amounts of non-renewable energy and emit toxic fumes. Thus, geothermal heat pumps have been proposed as a more energy-efficient substitution for diesel boilers. Currently, most horticultural facilities in the United States use shallow geothermal systems, and are often equipped with horizontal underground heat exchangers as well as heat pump equipment. These shallow geothermal systems require a large drilling site and heat pump to function, which results in high maintenance costs. The heat pump itself consumes a large amount of power, which degrades system performance. Conversely, high temperatures can be attained within a single borehole in deep geothermal vertical closing systems without using a heat pump. This setup can dramatically reduce the power consumption and improve system performance. In this study, we have modeled a circulation simulator after the circulation systems in deep geothermal facilities to analyze a 2000-meter borehole in Naju-Sanpo-myeon. The simulator is operated by manipulating various putative parameters affecting system performance to analyze the system's coefficient of performance.

Performance analysis of liquid flooded compression with regeneration for cold climate heat pumps

In regions with sub-freezing winter temperatures, the performance of conventional air-source vapor compression heat pumps drop drastically during extended periods of low outdoor ambient temperatures. Modifying the basic cycle configuration with liquid flooded compression and regeneration reduces the thermodynamic inefficiencies associated with the heat pump equipment and increases energy efficiency with less degradation in heating capacity especially at low ambient temperatures. Flooding non-volatile liquid along with refrigerant vapor stream into the compressor leads to a near isothermal compression process and thereby reduces desuperheating losses in the condenser. Regeneration improves the system performance by reducing throttling losses in the expansion device. The performance of a heat pump operating with flooded compression and regeneration has been analyzed for three sub-freezing outdoor ambient climatic regions: Boston, Indianapolis and Minneapolis. The results indicate that at −10 °C ambient temperature, COP (heating) of the flooded compression with regeneration cycle was approximately 13% higher than the standard vapor compression cycle. The Heating Seasonal Performance Factor (HSPF) of a flooded compression with regeneration cycle for Boston, Indianapolis and Minneapolis was approximately estimated to be 9%, 10% and 13% higher than the standard vapor compression cycle respectively.

Технико-экономические аспекты применения теплонасосного оборудования на объектах метрополитена

Технико-экономические аспекты применения теплонасосного оборудования на объектах метрополитена

Study of Heat-source-Tower Heat Pump System Efficiency

This paper introduced the forms and characteristics of heat-source-tower heat pump air-conditioning system, analyzed its principle and working process, established closed source heat pump equipment and studied on the influence of heat source heat pump performance under different outdoor air parameters, making antifreeze and water as the heat transfer medium. Studies have shown that the wet-bulb temperature is 3.6°C, relative humidity is 80%, and it need to be sprayed antifreeze for frost prevention and at this time the system efficiency has increased 5% to 11%, suggesting that heat source heat pump can increase its efficiency under frost prevention conditions, which would provide guidelines for designing heat-source heat pump system.

Technical and Economic Aspects of Using Heat Pump Systems for Heating and Cooling of the Moscow Subway's Facilities

This paper contains the results of research, carried out with financial support from the Ministry of Education and Science of the Russian Federation and dedicated to improving the energy efficiency of Moscow subway facilities and creation of stations with "zero" external sources heat consumption. This paper vindicates the possibility and economic feasibility of creating subway facilities with "zero" external sources heat consumption, equipped with heat pump systems for heating and cooling, which improve indoor climate comfort of subway's stations and halls. The research carried out by the authors proves the efficiency of using heat pump systems for heating and cooling in the Moscow subway. The proposed technology requires lower nonrecurrent capital investments than traditional technology, as well as enables to save up to 80 % of energy. Considering the current prices for connecting to the centralized heating systems, the technology in question pays back at the stage of construction. The possibility of stabilizing thermal conditions at stations and in halls of the subway is an important advantage of this technology. Tis paper proposes schemes of heat pump equipment usage that allows reversing it for operation in cooling mode, which provide sufficient air conditioning and humidity control at stations, halls and service rooms. The authors evaluate the heat emission of passengers, that is removed with the exhaust air, to be about 0.15-0.17 billion kW*h annually. Thus the Moscow subway just dumps outside about 2.4 billion kW*h of thermal energy, including heat emitted by passengers, annually. If recycled this amount of energy is sufficient to cover all subway's requirements for thermal energy.

Combined system of solar heating and cooling using heat pump

The heating and cooling systems of apartment buildings based on combined solar heat-pump equipment has been considered and the procedure of calculating its parameters has been worked out. A technical-economic analysis has been performed and compared with the boiler-setting version.

Modified Criterion for Economic Efficiency Estimation of Heat Pumps

In this work the cost-effectiveness of coal mine waste water low potential heat utilization and integration in the enterprise local heating network by the bivalent parallel scheme is investigated. It is shown that the additive criterion of economic efficiency is not always sensitive to the target value because of the reason of non-linear coupling between the arguments of the target function. Several cases were considered from the viewpoint of cost-effectiveness criterion. Moreover, the arguments of the target function are also nonlinear, depending on technological parameters of the heat pump (HP) equipment. As a more effective criteria were proposed the modified canonical additive-multiplicative function and Kolmogorov-Gabor polynomial function to obtain the generalized multivariate estimation of alternatives in two stages procedure.

Performance analysis of short helical borehole heat exchangers via integrated modelling of a borefield and a heat pump: A case study

This paper presents a new simulation tool package that calculates the energy efficiency of an entire Ground Source Heat Pump (GSHP) system. The package consists of two detailed models of borehole heat exchangers and heat pump equipment coupled in a single well-integrated calculation tool.It was used to analyze two types of ground heat exchangers in the same operating conditions for two Italian climates. Research focused on comparing a short helical-shaped pipe configuration with the more widespread and longer double U-tube. Analysis was carried out at the same energy exchange rate with the ground and addressed the difference in total borehole depth. The package also took into account the effects of the weather on the heat transfer between the heat exchanger and the surrounding ground.Analysis found that a much shorter total borehole depth was needed for the helical-shaped pipe, which consequently reduces installation costs. Therefore, this configuration may be a suitable alternative to conventional U-shaped tubes, especially for new residential housing with low energy loads and where deep probe drilling is not possible. Finally, this paper also investigates the influence of the axial effects in the ground on the seasonal energy efficiency of the whole system.

Study of Wood Drying with Two-Stage Compression High Temperature Heat Pump

In order to enhance the quality of woodwork, a new drying equipment of two-stage compression high temperature heat pump was developed. This heat pump drying equipment is capable of switching between one-stage compression and two-stage compressing. Components and working principle of two-stage compression high temperature heat pump equipment were introduced in this study. Drying experiment was conducted with Pinus massoniana plates. The results show that this equipment had great energy saving performance and the average energy recycling rate could be achieved beyond 28%. Meanwhile, by means of two-stage compression and utilization of new refrigerant-R245fa, condensing temperature and heating temperature reach 120 and 110°C, respectively.

Energy Savings through Variable Speed Compressor Heat Pump Systems

In the present study, four different kind of HVAC systems based on heat pump technology at three site locations (Milan, Rome and Palermo) were implemented and simulated. The simulated HVAC systems consisting of: ground source borehole (W-W (bh)); ground water wells (W-W(well)); air to water (A-W); air to air (A-A) heat pump systems applied for heating and cooling applications in a low energy residential building. In particular, the study is focused on comparative performance of single speed and variable speed compressor equipments based on heat pump technology. In this respect, the chosen site locations characterize the typical climatic zones of Italy (Milan-Continental, Rome-Intermediate and Palermo-Mediterranean). The results demonstrated that variable speed equipments can achieve considerable energy savings especially in the air source heat pump system applications. The estimation pointed out that variable speed heat pump equipment can enhance energy savings in comparison to constant single speed equipments especially at Palermo and Rome, in particular during heating season where most of the time, the equipments operate at lower part load ratios (PLR).