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ground-heat-exchangers
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Assessment and comparison of different arrangements of horizontal ground heat exchangers for high energy required applications
, Article Applied Thermal Engineering ; Volume 167 , 2020 ; Habibi, M ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Horizontal ground heat exchangers (GHEs) have a lower initial installation cost in comparison to vertical ones; however, they require more land area. In order to reduce the required land area of horizontal GHEs, their heat exchange rate per unit land area needs to be enhanced. A remedy to this problem is installing horizontal GHEs in an arrangement with maximum heat exchange rate per unit land area. However, such arrangements have not been introduced for different types of horizontal GHEs thus far. To this end, in this study, the thermal performance of various GHE pipe arrangements for three different types (linear, spiral, and slinky) of horizontal GHEs is evaluated. Comparing the obtained...
A numerical study on utilizing horizontal flat-panel ground heat exchangers in ground-coupled heat pumps
, Article Renewable Energy ; Volume 147 , March , 2020 , Pages 996-1010 ; Amadeh, A ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Horizontal ground heat exchangers (GHEs) have a lower cost in comparison to vertical ones; however, they require more land area. For the sake of reducing the required land area for horizontal GHEs, flat-panel GHEs have been recently introduced. In this piece of research, a 3-D numerical model has been developed to predict the thermal performance of flat-panel GHEs. In this study, at first, the thermal performance of a flat-panel GHE has been compared with that of linear horizontal ones. The results demonstrate that the flat-panel GHE has a better thermal performance of about 27% in comparison to an arrangement of linear GHEs with a value of 0.5 m for pipe spacing. In the second part of this...
A hybrid analytical-numerical model for predicting the performance of the Horizontal Ground Heat Exchangers
, Article Geothermics ; Volume 101 , 2022 ; 03756505 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Horizontal Ground Heat Exchangers (HGHE) as a means of exploiting geothermal energy has come to the fore for a few decades. Various analytical and Computational Fluid Dynamics (CFD) methods have been proposed to predict the performance of the HGHEs. The available analytical approaches are fast; however, they are based on various simplifications and assumptions, affecting their accuracy. On the other hand, CFD methods are more accurate, but their computational cost is a burden. Therefore there is an acute need for an accurate and fast method for predicting the long-term performance of HGHEs. To this aim, this study puts forward a novel hybrid analytical-numerical model for predicting the...
Thermal-economic Modeling and Optimization of Ground-Coupled Heat Pump System for Various Climatic Conditions of Iran
, M.Sc. Thesis Sharif University of Technology ; Abbaspour Tehrani Fard, Madjid (Supervisor)
Abstract
The optimal design of a ground-coupled heat pump (GCHP) system with vertical ground heat exchanger (VGHX) includes thermal modeling of the system and selection of optimal design parameters is presented in this research. Then, by applying Nelder-Mead optimization algorithm, an objective function (Total Annual Cost which is the sum of annual investment and operating costs of the system) is defined and minimized, exposed to specified design constraints. Also, Genetic Algorithm is used to verify the optimal design process. In order to evaluate the accuracy of a presented model, the optimum values of a heat pump design parameters includes saturated temperature/pressure of a condenser and...
Numerical Simulation of Horizontal Spiral Heat Exchangers for Ground Source Heat Pumps
, M.Sc. Thesis Sharif University of Technology ; Hakkaki-Fard, Ali (Supervisor)
Abstract
In recent years horizontal Ground Heat Exchangers (GHEs) has attracted a growing interest as heat source/sink for ground source heat pump systems. Horizontal GHEs initial installation costs are lower than the vertical ones; however, they require larger land area and more pipes. Therefore, it is necessary to reduce their required land area and pipe length by improving their thermal performance. In this study, a numerical modal based on 3-D simulation of GHE with computational fluid dynamics methods is developed. The model is used to evaluate the thermal performance and initial installation cost of horizontal GHEs. Four different types of horizontal GHEs: linear, spiral, horizontal and...
Effect of Ground Thermal Recovery Using Daily Temperature Difference on Performance of Ground Source Heat Pump
, M.Sc. Thesis Sharif University of Technology ; Hakkakifard, Ali (Supervisor)
Abstract
Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE...
Evaluation and improvement of the thermal performance of different types of horizontal ground heat exchangers based on techno-economic analysis
, Article Energy Conversion and Management ; Volume 171 , 2018 , Pages 1177-1192 ; 01968904 (ISSN) ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In recent years horizontal Ground Heat Exchangers (GHEs) has attracted a growing interest as heat source/sink for ground source heat pump systems. Horizontal GHEs initial installation costs are lower than the vertical ones; however, they require larger land area and more pipes. Therefore, it is necessary to reduce their required land area and pipe length by improving their thermal performance. In this study, a numerical modal based on 3-D simulation of GHE with computational fluid dynamics methods is developed. The model is used to evaluate the thermal performance and initial installation cost of horizontal GHEs. Four different types of horizontal GHEs: linear, spiral, horizontal and...
In pursuit of a replacement for conventional high-density polyethylene tubes in ground source heat pumps from their composites – a comparative study
, Article Geothermics ; Volume 87 , September , 2020 ; Fatehifar, M ; Ghasempour, R ; Noorollahi, Y ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Ground-source heat pumps, as the most environmentally friendly and energy-efficient air conditioning technology, suffer from a great required length of ground heat exchanger, partly arising from the low thermal conductivity of high-density polyethylene tubes commonly used in ground heat exchangers. In an attempt to find a replacement with an acceptable thermal conductivity for high-density polyethylene tubes, in this study, first, a comprehensive comparative study on fillers commonly used in thermally conductive polymer composites and resulting high-density polyethylene composites was conducted. Then, based on the advantages and disadvantages presented, an appropriate composite was selected...
A novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate
, Article Energy Conversion and Management ; Volume 224 , 2020 ; Habibi, M ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE...
Thermal performance analysis of an energy pile with triple helix ground heat exchanger
, Article Geothermics ; Volume 104 , 2022 ; 03756505 (ISSN) ; Asgari, B ; Rostami, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
A Ground Source Heat Pump (GSHP) is a renewable energy-based HVAC system that extracts or supplies heat from/to the ground via a Ground Heat Exchanger (GHE). One of the most commonly used types of GHE in GSHP systems is the energy pile. In this realm, the GSHP system with a triple helix energy pile has become the focus of attention. To this aim, a comprehensive three-dimensional transient Computational Fluid Dynamics model of the energy pile with triple helix GHE and the surrounding soil is developed. The effect of several parameters, including helix pitch, helix diameter and pipe diameter, on the thermal performance of the system, is investigated. Simulated cases are chosen using the design...
On the thermal performance enhancement of spiral-coil energy piles with a thermal recovery system
, Article Energy and Buildings ; Volume 269 , 2022 ; 03787788 (ISSN) ; Asgari, B ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
The pile foundation designed to ensure building stability when equipped with heat exchanger pipes to harvest geothermal energy is called an energy pile. Ground Source Heat Pump (GSHP) systems combined with energy piles have been used and developed as sustainable and efficient HVAC systems. Energy piles suffer from cold or heat accumulation in and around the pile, degrading their long-term performance. The current study seeks to alleviate this problem by proposing a thermal recovery system. The proposed system circulates ambient air in the pile foundation to extract the accumulated heat. A three-dimensional transient computational fluid dynamics model of the GSHP system coupled with the...
Modeling of a Hybrid Ground Source Heat Pump System with Solar Thermal Collector and Phase Change Materials
, Ph.D. Dissertation Sharif University of Technology ; Abbaspour, Majid (Supervisor) ; Saeedi, Mohammad Hassan (Supervisor)
Abstract
In recent years, ground source heat pumps (GSHPs) have received increasing attention for space heating and cooling, and domestic hot water production due to their high energy performance and low environmental impacts. The most common type of ground heat exchanger used in the GSHP systems is borehole heat exchanger (BHE) that consists of U-shaped tubes placed in the vertical boreholes. In this system, the heat is absorbed from or rejected to the ground by circulation of a fluid through the ground loop. The GSHP systems provide high seasonal performance factors when the ground loads are well balanced over the year. However, most buildings in cold or hot climates have unbalanced loads. When the...
Estimation of Ground Thermal Properties Using Inverse Heat Transfer Techniques
, M.Sc. Thesis Sharif University of Technology ; Hakkakifard, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor) ; Biglarian, Hassan (Co-Supervisor)
Abstract
Ground-Source Heat Pumps (GSHPs) are efficient means of space heating and cooling. However, owing to their high installation costs, their development in societies has not grown as it should. Therefore, it is crucial to have a meticulous design of these systems. The first step in designing GSHPs is determining the ground and grout thermal properties. Thermal Response Tests (TRTs) are developed for this purpose. The previous methods of estimating the unknown thermal properties are either computationally inefficient or yield inaccurate estimates for the ground volumetric heat capacity, to which the mean fluid temperature has the slightest sensitivity among all thermal properties. Among previous...
Technical assessment of ground-source, air-source, and hybrid heat pumps for single-family buildings in cold climates
, Article 25 June 2016 through 29 June 2016 ; Volume 122 , 2016 , Pages 270-280 ; 00012505 (ISSN) ; 9781939200464 (ISBN) ; Hakkaki Fard, A. M ; Aidoun, Z ; Ouzzane, M ; Sharif University of Technology
Amer. Soc. Heating, Ref. Air-Conditoning Eng. Inc
Abstract
This paper discusses a technical comparison of a directexpansion ground-source heat pump (DX-GSHP) and an airsource heat pump (ASHP). To lower the ground heat exchanger size for cost reduction purposes, the system performance of a hybrid system is also evaluated using a supplementary air evaporator combined with the DX-GSHP. Detailed screening models previously developed for ASHPs and DX-GHSPs are first used to compare the seasonal performance of these two options for a residential building in the cold-climate city of Montreal, Canada. Then, the model is adopted for performance evaluation of the hybrid system. Additionally, different parameters including borehole total length and heat pump...
A numerical model for transient simulation of borehole heat exchangers
, Article Renewable Energy ; Volume 104 , 2017 , Pages 224-237 ; 09601481 (ISSN) ; Abbaspour, M ; Saidi, M. H ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
A numerical model is developed to simulate the borehole heat exchanger both in the short and long time. In this regard, the computational domain is divided into the inside and outside borehole regions. A two-dimensional finite volume method is implemented in a cylindrical coordinate system for modeling of the outside borehole. Also, a thermal resistance-capacity model is presented for the borehole cross section. This model is extended to take into account the fluid transport through the U-tube and the temperature variation of the borehole components with depth. The governing equations of the two regions are solved iteratively in each time step. The proposed model is verified with the...
Studying the Effect of Using Zeotropic Refrigerant Mixtures on the Performance of the Vertical Ground Coupled Heat Pump
, M.Sc. Thesis Sharif University of Technology ; Hakkaki Fard, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Supervisor)
Abstract
Vertical ground-coupled heat pumps due to using a renewable energy stored in the ground and being away from ambient temperature fluctuations have a good coefficient of performance and very low pollution. Despite these advantages, these systems have not gained a pervasive position in the field of heating/cooling systems due to their high initial cost. Despite these advantages, these systems have not gained a pervasive position among communities due to their high initial cost. In the present project, a comprehensive study has been conducted to investigate the effect of using zeotropic refrigerant mixtures on the performance of vertical ground-coupled heat pumps and reducing its initial costs....
On the Performance of the Geothermal Dehumidifier of the Solar-Driven Hdh Desalination System: a Numerical Study
, M.Sc. Thesis Sharif University of Technology ; Hakkakifard, Ali (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Supervisor)
Abstract
The solar-driven humidification-dehumidification desalination system with a geothermal dehumidifier (SD-HDH-GD) has been given special attention, for producing drinking water and subsurface irrigation applications. This contribution scrutinizes the performance of the geothermal dehumidifier of the SD-HDH-GD system. To this aim, a comprehensive three-dimensional transient computational fluid dynamics model of the geothermal dehumidifier and the surrounding soil is developed. An experimental setup is established to verify the developed numerical model. At first, the performance of the system in a short-term period of 12 hours is investigated, and the effect of several operation parameters is...