AP08857319 «Study of heat transfer enhancement mechanisms of vertical type borehole heat exchanger to ensure high heat pump performance»

The relevance of the project.

Today, ground source heat pumps (GSHP) are recognized as one of the sustainable heat supply technologies in continental climate regions [1-2], due to the fact that the soil temperature does not have large changes depending on the seasons compared to atmospheric air. According to the International Energy Agency (IEA), heat pumps are classified as heating and cooling systems using renewable energy sources ( https://www.eu4energy.iea.org/ ). At the same time, heat pumps can be categorized as energy efficiency technology. However, existing GSHP lose their coefficient of performance (COP) over the years. Several factors are responsible for the decrease in COP of GSHP: a decrease in low potential soil heat without restoring the extracted heat, insufficient consideration of the geological and thermophysical properties of the soil, insufficient design of ground source heat exchangers (GSHX) taking into account the understanding of physical processes in the soil. The latter is associated with the engineering calculations of installers, which may not be enough for some conditions (the presence of groundwater seepage, flow directions, etc.). In this regard, during the installation of GSHP, it is necessary to understand the fluid flow and heat transfer processes occurring in the GSHX and soil. Consideration of these components will make it possible to correctly simulate GSHX with the possibility of heat storage and restoring the thermal properties of the soil, taking into account the geometric parameters of GSHX, and select an efficient “Water-to-Water” heat pump. In order to answer these questions, it is necessary to apply the methods of computational fluid dynamics (CFD) and heat transfer.

The proposed project aims to study the mechanisms for increasing the heat transfer characteristics of a vertical borehole GSHX to increase the COP of a heat pump for the purpose of space heating/cooling and hot water supply. Additionally, the GSHX in the summer season in the presence of excess heat from the solar water heating system and waste heat from the heat pump in the room cooling mode has the ability to store heat in the ground in order to restore and increase its thermal properties. This method will increase the thermal performance (COP) of the heat pump in the heating season. These goals will be achieved by studying various geometric configurations of a borehole GSHX based on numerical simulation of fluid dynamics and heat transfer processes, thermodynamic analysis, and engineering modeling methods. Also, based on the calculated data, one experimental prototype of the most efficient configuration of a GSHP will be assembled. Based on the research results, recommendations will be developed on the installation and operation of a GSHP for heat supply in continental climate regions.              

The main objective of the project:

The Project goal is to study a heat transfer enhancement mechanisms of borehole heat exchangers to increase the heat pump performance and develop recommendations. The recommendations will be based on measurements of the ground source heat pump, on fluid dynamics and heat transfer calculations using licensed software and own algorithms.

Expected results

1) Mathematical Modeling and Design

1.1) A ground source heat pump prototype schematic with a vertical borehole ground source heat exchanger will be developed.

1.2) Mathematical modeling of fluid dynamics and heat transfer processes using CFD methods will be carried out using licensed software and computer algorithms of our own design to identify efficiency operational modes of a ground source heat exchanger taking into account the thermal properties of the soil.

1.3) Numerical calculations of fluid dynamics and heat transfer processes in a vertical ground source heat exchanger of various geometric configurations will be carried out to identify the most efficient heat transfer modes.

2) Assembly and Testing

2.1) One most efficient ground source heat exchanger configuration will be created.

2.2) The energy-efficient operatinal modes of the ground source heat exchanger will be determined.

2.3) A “Water-to-Water” heat pump will be created and connected to a ground source heat exchanger.

2.4) The efficient operational characteristics of the ground source heat pump will be determined: the heat pump coefficient of performance (COP) in heating/cooling mode, the efficiency of the ground source heat exchanger with heat storage, and the heat load of the test room.

3) Monitoring and Analysis

3.1) The energy efficiency and thermal performance of a ground source heat pump will be monitored.

3.2) The energy and exergy efficiency of the ground source heat pump will be determined based on the first and second law thermodynamic analysis.

3.3) Recommendations will be developed on the installation and operation of a ground source heat pump with heat storage.

3.4) A market analysis of the heat pump in Kazakhstan will be prepared and a search will be made for ways to the technology commercialization.

Achieved results:

For the first time, problems of approximation of the microscopic Maskwell boundary condition, which depends on the surface temperature of the moving boundary, for the distribution function in the case of a one-dimensional non-stationary nonlinear Boltzmann equation containing an unknown parameter as the speed of the aircraft, and the correctness of the initial-boundary value problem for a one-dimensional non-stationary nonlinear system of moment equations in the third approximation under macroscopic Maxwell-Aughan boundary conditions, are studied for the first time. Determining the aerodynamic characteristics of an aircraft using a system of moment equations in the third approximation under macroscopic boundary conditions is a new unexplored problem in rarefied gas dynamics.

Names and surnames of the members of the research group with their identifiers:

  1. Belyaev Erzhan Kelesovich – scientific supervisor
  2. Erdesh Elnar Bakhytkhanuly – researcher
  3. Toleukhanov Amankeldi Eleshevich– leading researcher
  4. Aliuly Abdurashid - researcher
  5. Shakir Esen Kairat - researcher
  6. Seitov Abzal Niyazbekuly - researcher
  7. Amanzholov Tannur Ersinuly- researcher
  1. List of publications:

1. Yang L.W., Xu R.J., Hua N., Xia Y., Zhou W.B., Yang T., Belyayev Ye., Wang H.S. Review of advances in solar-assisted air source heat pumps for the domestic sector // Energy Conversion and Management. – 2021. - vol. 247. – 114710 (Impact Factor 9,709).

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