Design Of Pump System Research Articles

Field demonstration of a first thermal response test with a low power source

Thermal response tests conducted to assess the subsurface thermal conductivity for the design of ground-coupled heat pump systems require a power source of about 7–12 kW to heat water circulating in a ground heat exchanger. This high power is commonly supplied with a fuel-fired generator, which is an important source of cost. An alternative method relying on a power source of less than 1 kW was consequently developed and used for a first field demonstration. Heat was injected along ten short sections of heating cable standing in the water column filling the pipe of the exchanger. Recovery temperatures measured at the middle height of each heating section were analyzed with a linear heat source solution of finite length. The ten local measurements distributed over a depth of 139 m and averaged according to the site stratigraphy revealed a subsurface thermal conductivity that is within an acceptable range of the bulk value determined with a conventional test. The new method has the potential to reduce the use of generators for thermal response tests since a low power source is common to construction sites.

An improved evaluation method for thermal performance of borehole heat exchanger

Thermal performance of vertical U-pipe borehole heat exchanger (BHE) is an important research subject for the design and application of ground-coupled heat pump system (GCHPs). This paper presents an improved evaluation method for thermal performance of BHE based on analytical solution model, which is validated by comparing with duct storage system (DST) model and field experiment. Using the evaluation method, impacts of inlet fluid temperature, fluid flow rate and borehole depth on thermal performance of two types of U-pipe BHEs are studied. The study provides a good alternative of the experimental method for thermal performance test (TPT) and a useful thermal performance evaluation tool for BHEs in GCHPs.

Experimental validation of a short-term Borehole-to-Ground (B2G) dynamic model

The design and optimization of ground source heat pump systems require the ability to accurately reproduce the dynamic thermal behavior of the system on a short-term basis, specially in a system control perspective. In this context, modeling borehole heat exchangers (BHEs) is one of the most relevant and difficult tasks. Developing a model that is able to accurately reproduce the instantaneous response of a BHE while keeping a good agreement on a long-term basis is not straightforward. Thus, decoupling the short-term and long-term behavior will ease the design of a fast short-term focused model. This work presents a short-term BHE dynamic model, called Borehole-to-Ground (B2G), which is based on the thermal network approach, combined with a vertical discretization of the borehole.The proposed model has been validated against experimental data from a real borehole located in Stockholm, Sweden. Validation results prove the ability of the model to reproduce the short-term behavior of the borehole with an accurate prediction of the outlet fluid temperature, as well as the internal temperature profile along the U-tube.

Thermal conductivity map of the Oslo region based on thermal diffusivity measurements of rock core samples

A thermal conductivity map can serve as a good basis for ground-source heat pump projects in the pre-design phase. However, due to large variations, a thermal response test is required for larger projects to get the accurate values needed for proper design of the ground-source heat pump system. This study describes the systematic methodology for producing such a thermal conductivity map of a larger geographic area around Oslo, Norway. The map is based on the results of 1,398 thermal diffusivity measurements of rock core samples. The thermal diffusivity is measured and used in the calculation of the thermal conductivity of the different geological units in the bedrock map of the Oslo region. Large variations in thermal conductivity data were registered within the data sets for the different rock polygons and geological units and the greatest variation is found in metamorphic and sedimentary rocks. Rock polygons and geological units with magmatic origin show the least variation within the data sets. The internal micro structures of the rocks can have a strong influence on the thermal conductivity. This is pronounced in some foliated metamorphic rocks where the thermal conductivity is highest parallel to the orientation of the foliation. The median value for the whole data set is 2.62 W/(m K), while the minimum and maximum value is 1.0 and 6.88 W/(m K), respectively. The minimum value is a breccia, and the maximum value was measured in a quartzite/metasandstone. The lower and upper quartiles for the sets of rock polygons and geological units are 2.1–3.9 W/(m K), respectively.

Hydrogeology and design of groundwater heat pump systems

Groundwater can serve as an environmentally friendly and renewable energy source when utilized in a groundwater heat pump system. Installation of such systems has been increasing worldwide in recent years. Performance of a groundwater heat pump system depends on local hydrogeological and thermo geological conditions. It is important that aquifer properties be determined to be representative of the site when designing a system in order to maximize efficiency, reduce installation costs, and minimize any environmental impacts. Factors that need to be considered are the groundwater temperature profile to the depth at which the temperature becomes relatively stable; hydraulic and thermal conductivities; diffusivity of the soil and rock layers; groundwater levels; and groundwater quality. Selection of groundwater and heat pump coupling techniques relies on, to a large extent, an accurate conceptual site scale model of groundwater conditions and understanding of environmental and legal constraints.

Numerical simulation for the optimum design of ground source heat pump system using building foundation as horizontal heat exchanger

Ground source heat pump system takes advantage of the stable ground temperature to achieve energy savings and to reduce CO2 emission. However, the system has several barriers for the wider application such as high installation costs, incompletion of design standard and lack of recognition as heating and cooling system. In order to solve the problems, the energy-foundation system was developed by several researches which use building foundation as a heat exchanger. Although many construction companies have more interest in various types of energy-foundations, there are few researches on the design method. In this study, in order to establish the optimum design tool of an energy-foundation system integrated with the horizontal heat exchanger, the prediction method of ground heat exchange rate was developed with numerical simulation model. The developed model was coupled with ground heat transfer model, ground surface heat model and ground heat exchanger model. Furthermore, case studies on prediction of heat exchange rate (HER) have been conducted at different conditions of design and installation with variables such as pipe spacing, installation depth, pipe diameter, circulation water temperature, flow rate, and operation condition. The HER for each case study has been calculated based on the long-term simulation.

A p(t)-linear average method to estimate the thermal parameters of the borehole heat exchangers for in situ thermal response test

The p-linear average method has been developed to estimate the ground thermal parameters for the design of a Ground-Coupled Heat Pump (GCHP) system, including the ground thermal conductivity, the ground thermal diffusivity and the borehole thermal resistance. Conventionally, the parameter p is considered as a constant, although essentially its value varies with time. To deal with the variation of the p value, this paper proposes a new approach, titled as p(t)-linear average method, to estimate the ground thermal parameters as well as the p values at the different sampling times. The proposed method has been evaluated using the data collected from an in situ thermal response test (TRT). It is found that the proposed method leads to a 6.31% reduction of the borehole thermal resistance when compared to the conventional arithmetic mean temperature method (the p-linear average model with p=1). Besides, compared to the theoretical results, the maximum relative error in the borehole thermal resistance for the conventional arithmetic mean temperature method is as high as 40.69%. In contrast, the maximum relative error for the p(t)-linear average method is less than 3% for all the typical practical cases. Therefore, the proposed p(t)-linear average method is more accurate to be used to estimate the ground thermal parameters for the design of a GCHP system.

Analysis on the Technical Solutions of the Heat Source of the Geothermal Heat Pump System

Taking the geothermal heat pump system in the campus of Hunan University of Technology for example, three technical solutions of the heat source of the system were analyzed in terms of the condensing heat load, the annual unbalanced heat load and the energy efficiency ratio (EER) of the system. In addition, comparison was conducted among the solutions. The results indicate that the solution 3, which has a cold and hot water integrative unit and hot water unit connected in series, meanwhile has a cooling tower for auxiliary cooling, shows better performance among all the solutions. The analysis on the solution of heat source of geothermal heat pump system, which usually contains the analysis on the condensing heat load, annual unbalanced heat load and EER, is of great significance for the design and development of the geothermal heat pump system with lower coat and higher EER.

Total Energy Consumption Optimization Design of Surface-Water Source Heat Pump Systems

This paper deals with the study of transmission and distribution energy consumption (TDEC) optimization design about surface-water source heat pump system. Three mathematical model have been established. The fitted polynomials of COP, Ne, Nc were obtained by the MATLAB curve fitting toolbox according to datum from product samples. The differences between two operating states which are constant flow and variable flow were analyzed and compared. Under variable flow operating state it was found that there exists an maximum energy conversation rate12.68% of TDEC; the heat pump unit will consume more than average 8.41% energy, while COP will decline average 7.61%, the mean energy conversation rate of Ne and Nc are 49.38% and 38.86%, the average declination rate of tein and tcout are 17.09% and 5.73% compared with constant flow operating state.

Analysis on Heat Transfer Energy Efficiency of U-Tube Buried Pipe under Variable Entering Water Temperature Conditions

Taken as the carrier of heat extraction between rock-soil body and ground source heat pump systems, U-tubed pipe heat transfer efficiency was the key for ensuring the long-term and high-performance operation of ground source heat pump systems by means of improving the heat transfer effect. The efficiency coefficient, E, is defined as the ratio of the actual heat transfer capacity to the theoretically maximal heat transfer capacity from the U-tube into rock-soil body, which illustrated the effect of heat transfer ability and the variable heating or cooling loads. Aim at Variation characteristics of heat transfer coefficient of energy efficiency under the variable temperature inflow condition, decomposed into the product of the ratio of biggest buried tube heat transfer temperature difference φ and heat pump outlet water temperature difference σ. Use of u-shaped buried pipe three-dimensional heat transfer model which based on the multipole theory, the influence law of its change which caused by the construction load, buried pipe flow and the unit performance were analyzed, it can provide technical support to optimize the design of ground source heat pump system.

Design of rural photovoltaic water pumping systems and the potential of manual array tracking for a West-African village

Photovoltaic (PV) power systems are attractive for use with water pumping systems in remote, off-grid areas with naturally high solar insolation. Two simplified design procedures for these systems are reviewed and compared to a more detailed analysis for a specific village (Ying, 9.7°N, 0.8°W) in West Africa. The simple design methods result in too little flow during months with below-average insolation. A rule-of-thumb chart is presented to predict flow losses for similar installations. To explore possible benefits of tracking strategies, ten different array configurations were simulated: three with fixed orientation, six with single axis tracking, and one with dual axis tracking. Of the three fixed orientation arrays, the configuration to maximize insolation and flow was an equator-pointing array with slope slightly greater than local latitude. The single and dual axis trackers were simulated with seasonal, monthly, and hourly tracking periods, the latter being a good representation of a continuous tracking system. For single axis tracking, a vertical axis array with slope fixed at 30° and variable azimuthal angle provided the best performance. For dual axis tracking, hourly array re-orientation results in significantly more received insolation (17.6% greater than non-tracking horizontal array) while adjustments only on a seasonal or monthly basis still yield 8.5% relative gain. In general, there is little predicted difference between monthly and seasonal re-adjustment of array orientation. A single vertical axis variation allows almost the same benefit as a full two-axis variation if re-oriented on a monthly or seasonal basis. Using one of these strategies could translate into reduced array size, reduced capital costs, or could provide extra margin for future increased water flow requirements due to community growth or unexpected weather. Simple monthly or seasonal adjustment by residents also could increase the sense of ownership in those served by the system.

A Study on the Calculation Model of Rock Soil Thermal Conductivity in the Design of the Ground Source Heat Pump System

The rock soil thermal conductivity is the most important design parameter for the ground source heat pump system. Based on the equation applied for the heat transfer between the geothermal heat exchanger and its surrounding rock soil, a quasi-three dimensional heat conduction model showing the heat transfer inside the borehole of the U-tube was established to determine the thermal conductivity of the deep-layer rock soil. The results obtained show that the average thermal conductivity got through calculation and actual determination in a tube-embedding region of the ground source heat pump engineering were 1.895 and 1.955W/(m·°C), respectively. The soil layer, which has a great thermal conductivity and a strong integrated heat transfer capability, is suitable for the use of the ground source heat pump system with the tubes embedded underground. The soil layer, with a body temperature of 19 °C and a higher initial temperature, is suitable for the heat extraction from underground in winter. The deviation between the calculation and the determination of the average thermal conductivity in the abovementioned region was 0.06, which could meet the required precision, indicating that the results from the calculation could be used for design.

Flow characteristics of the raw sewage for the design of sewage-source heat pump systems.

The flow characteristics of raw sewage directly affect the technical and economic performance of sewage-source heat pump systems. The purpose of this research is to characterize the flow characteristics of sewage by experimental means. A sophisticated and flexible experimental apparatus was designed and constructed. Then the flow characteristics of the raw sewage were studied through laboratorial testing and theoretical analyses. Results indicated that raw sewage could be characterized as a power-law fluid with the rheological exponent n being 0.891 and the rheological coefficient k being 0.00175. In addition, the frictional loss factor formula in laminar flow for raw sewage was deduced by theoretical analysis of the power-law fluid. Furthermore, an explicit empirical formula for the frictional loss factor in turbulent flow was obtained through curve fitting of the experimental data. Finally, the equivalent viscosity of the raw sewage is defined in order to calculate the Reynolds number in turbulent flow regions; it was found that sewage had two to three times the viscosity of water at the same temperature. These results contributed to appropriate parameters of fluid properties when designing and operating sewage-source heat pump systems.

Discussion of Ground Source Heat Pump System Heat Balance in Severe Cold Area

This template comprehensive analysis of the causes of soil heat balance, heat balance of soil caused by the results, heat balance of soil factors influence, several domestic thermal imbalance of soil heat balance and common measures to solve the problem, for the future of the soil source heat pump system design for the constructive suggestion.

고성능 히트펌프 해석모델 개발 연구

히트 펌프는 지열이나 태양열 등의 신재생 에너지를 이용하거나 기타 폐열을 재활용하여 기존의 전기 히팅 난방 시스템들보다 에너지 소비율을 낮출 수 있다는 장점으로 인해 그린 에너지 시스템으로써 주목을 받아 왔다. 고효율 히트펌프 시스템 설계를 위한 연구는 오랫동안 지속되어 왔지만, 각각의 구성요소가 유기적이며, 변화에 유연한 해석모델은 존재하지 않는다. 따라서 본 연구에서는 공기 열 원식 히트 펌프를 AMESim Software를 이용해 구성하였다. 독자적으로 개발한 스크롤 압축기 해석 모델을 히트펌프 시스템에 조합함으로써 효율 향상 방안을 모색하였으며, 실험 데이터를 이용하여 개발한 해석모델을 검증하였다. 실험 데이터와 개발한 해석 모델을 이용하여 예측된 데이터를 비교한 결과 최대 오차가 10% 이내로 두 데이터가 잘 일치하였다. 본 연구에서 개발한 히트펌프 해석모델은 향후 시제품을 개발하고 효율 향상을 위한 연구 등에 유용하게 사용될 것으로 사료된다. Heat pumps have attracted considerable attention as a green energy system because they use renewable energy, such as geothermal, solar energy and waste heat, and can have a low electricity consumption rate compared to other conventional electric heating system. Many studies of high efficient heat pump system design was performed previously,but it is not easy to find any an analytical model that consists of components (e.g. compressor, heat exchangers, and expansion valve), not only having an interrelation and interconnection each other but also being flexible to any change in geometry and operating parameters. In this study, a computational model was developed for a heat pump with warm air as a heat source using the one-dimensional modeling software, AMESim. In combination with an independently-developed analytical model for a scroll compressor, the heat pump model can simulate the physical characteristics and actual behavior of the heat pump precisely. In addition, the reliability of the model was improved by verifying the simulation results using experimental data. The simulation data fell into the 10% error range compared with the experimental data. The heat pump model can be used for system optimization studies of product development and applied to other applications in a range of industrial field.

Design and performance of main vacuum pumping system of SST-1 Tokamak

Steady-state Superconducting Tokamak (SST-1) was installed and it is commissioning for overall vacuum integrity, magnet systems functionality in terms of successful cool down to 4.5K and charging up to 10kA current was started from August 2012. Plasma operation of 100kA current for more than 100ms was also envisaged. It is comprised of vacuum vessel (VV) and cryostat (CST). Vacuum vessel, an ultra-high (UHV) vacuum chamber with net volume of 23m3 was maintained at the base pressure of 6.3×10−7mbar for plasma confinement. Cryostat, a high-vacuum (HV) chamber with empty volume 39m3 housing superconducting magnet system, bubble thermal shields and hydraulics for these circuits, maintained at 1.3×10−5mbar in order to provide suitable environment for these components. In order to achieve these ultimate vacuums, two numbers of turbo-molecular pumps (TMP) are installed in vacuum vessel while three numbers of turbo-molecular pumps are installed in cryostat. Initial pumping of both the chambers was carried out by using suitable Roots pumps. PXI based real time controlled system is used for remote operation of the complete pumping operation. In order to achieve UHV inside the vacuum vessel, it was baked at 150°C for longer duration. Aluminum wire-seals were used for all non-circular demountable ports and a leak tightness<1.0×10−9mbarl/s were achieved.

Diffusion, User Experiences and Performance of UK Domestic Heat Pumps

Heat pumps for space and water heating are recognised by EU governments as a key technology to meet carbon reduction and renewable energy targets, especially as electricity supplies are decarbonised. As a result of many socio-economic and technical factors, heat pumps are well-established in some EU countries, while in others including the UK, the market is immature. A field trial of heat pumps, found that, especially before specialist intervention, UK domestic heat pumps performed considerably less efficiently than those in Germany and Switzerland. This paper reports on the experiences and satisfaction of users in the field trial and the influence of technical and user factors on system efficiency. A comparative site analysis indicates that many interacting factors affect heat pump efficiency, including dwelling energy efficiency; heat pump system design and installation quality; and some of the characteristics and different heating behaviours of private householders and social housing tenants. The implications for low carbon energy policies, heat pump design and diffusion are discussed.

Optimizing the design of a geothermal district heating and cooling system located at a flooded mine in Canada

Flooded underground mines are attractive for groundwater heat pump systems, as the voids created during mining operations enhance the subsurface permeability and storage capacity, which allows the extraction of significant volumes of groundwater without requiring extensive drilling. Heat exchange at a flooded mine is, however, difficult to predict because of the complex geometry of the underground network of tunnels. A case study is presented here to demonstrate that numerical simulations of groundwater flow and heat transfer can help assess production temperatures required to optimize the design of a heat pump system that uses mine water. A 3D numerical model was developed for the Gaspe Mines located in Murdochville, Canada, where a district heating and cooling system is being studied. The underground mining tunnels and shafts are represented in the model with 1D elements whose flow and heat transfer contributions are superimposed to those of the 3D porous medium. The numerical model is calibrated to simultaneously reproduce the groundwater rebound that occurred when the mine closed and the drawdown measured during a pumping test conducted in a former mining shaft. Predictive simulations over a period of 50 years are subsequently performed to minimize pumping rate and determine maximum heat extraction rate.

지중 열교환기의 보어홀 열저항 산정에 관한 연구

최근 들어 경제적이고 친환경적인 에너지 활용을 위하여 지열에너지 필요성이 증대되고 있다. 지반의 열전도도(ground thermal conductivity)와 보어홀 열저항(borehole thermal resistance)은 지열 히트펌프 시스템(geothermal heat pump system)의 설계 과정에서 매우 중요한 변수이다. 본 논문에서는 일반 수직밀폐형에서의 U, W 타입의 지중 열교환기(ground heat exchanger)를 매립지 지반에 설치한 후 100시간 연속 운전 조건으로 현장 열성능 실험(thermal performance test)을 수행하였다. 또한 보어홀 열저항 산정 모델들을 이용하여 열효율을 산정한 후 이를 실험값과 비교하였다. 실험 결과 기존에 주로 적용되고 있는 shape factor(SF) 모델보다 multi-pole과 equivalent diameter(EQD) 모델이 계측값과 잘 일치하였다. The use of geothermal energy has been increased for economic and environmental friendly utilization. Ground thermal conductivity and borehole thermal resistance are very important parameters in the design of geothermal heat pump system. This paper presents an experimental study of heat exchange rate of U and W type ground heat exchangers (GHEs) measured by thermal performance tests (TPTs). U and W type GHEs were installed in a partially saturated dredged soil deposit, and TPTs were conducted to evaluate heat exchange rates under 100-hr continuous operation condition. The heat exchange rates were also calculated by analytical models to estimate borehole thermal resistances and were compared with experimental results. It comes out that multi-pole and equivalent diameter (EQD) models resulted in more accurate agreement than shape factor (SF) model which is currently more often used.

System modeling and building energy simulations of gas engine driven heat pump

To improve the system performance of a gas engine driven heat pump system, an analytical modeling and experimental study has been made by using a desiccant system in cooling operation (particularly in high-humidity operations) and suction line waste heat recovery to augment heating capacity and efficiency. The overall performance of a gas engine driven heat pump system has been simulated with a detailed vapor compression heat pump system design model. The modeling includes (1) a gas engine driven heat pump cycle without any performance improvements (suction liquid heat exchange and heat recovery) as a baseline (both in cooling and heating mode), (2) a gas engine driven heat pump cycle in cooling mode with a desiccant system regenerated by waste heat from the engine incorporated, and (3) a gas engine driven heat pump cycle in heating mode with heat recovery (recovered heat from engine). According to the system modeling results, by using the desiccant system, the sensible heat ratio can be lowered to 40%. The waste heat of the gas engine can boost the space heating efficiency by 25% at rated operating conditions. In addtion, using EnergyPlus, building energy simulations have been conducted to assess annual energy consumptions of the gas engine driven heat pump in 16 U.S. cities, and the performances are compared to a baseline unit that has a electrically driven air conditioner with the seasonal coefficient of performance of 4.1 for space cooling and a gas furnace with 90% fuel efficiency for space heating.