Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates

Design Principles, Potential Applications and Case Studies

Vasile Minea

• Verlag: CRC Press
• Jahr: 2022
• ISBN:
  9781000564310
• Auflage: 1
• Thema: Ciencias físicas
• Thema: Química industrial y técnica

Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates: Design Principles, Potential Applications and Case Studies focuses on applications and cases studies of ground-source heat pumps in moderate and cold climates. It details technical aspects (such as materials, thermal fluid carriers and pumping, and drilling/trenching technologies), as well as the most common and uncommon application fields for basic system configurations. The principles of system integrations and applications in moderate and cold climates (such as hybrid, solar-assisted, thermo-syphon, foundation, mines, snow melting, district heating and cooling ground-source heat pump systems, etc.) are also presented, each followed by case studies.

• 
  
  

• Based on the author's more than 30 years of technical experience

• 
  
  

• Discusses ground-source heat pump technologies that can be successfully applied in moderate and cold climates

• 
  
  

• Presents several case studies, including successful energy results, as well as the main lessons learned

This work is aimed at designers of HVAC systems, as well as geological, mechanical, and chemical engineers implementing environmentally-friendly heating and cooling technologies for buildings.

1 Introduction

DOI: 10.1201/9780367466589-1

Volume 2 of this book focuses on design principles, potential applications, and cases studies of ground-source heat pumps in moderate and cold climates. Technical aspects (as materials, thermal fluid carriers and pumping, and drilling/trenching technologies) are presented, as well as the most common and un-common application fields. The principles of system integrations and applications in cold and moderate climates (as solar-assisted, thermo-syphon, foundation, mines, snow melting, district heating and cooling ground-source heat pumps systems, and hybrid) are also discussed, each followed by representative case studies.

Chapter 2 presents some design principles for vertical (closed-loop, secondary fluid) ground-coupled heat exchangers for ground-source heat pump systems for residential and non-residential buildings, provides an outlook on design tools, and summarizes the main results of six case studies.

Chapter 3 first presents some common types of horizontal ground-coupled heat exchangers of closed-loop (indirect, secondary fluid) ground-source heat pump systems applied in residential and commercial/institutional buildings in cold and moderate climates, a number of basic design and installation principles, as well as some advantages and limitations. The main characteristics and main results of four case studies are finally summarized.

Chapter 4 summarizes some of the design and installation principles of open-loop groundwater heat pump systems, including aspects related to well construction, circulation pump, and selection of intermediate heat exchangers and building indoor water closed loops.

Chapter 5 presents some general design principles of open-loop, single well (standing column) ground-source heat pump systems, their main advantages and limitations, as well as a laboratory case study conducted in the Canadian eastern cold climate.

Chapter 6 first identifies a part of most critical design principles of horizontal closed-loop direct expansion ground-source heat pump systems and then presents the main results from four case studies.

Chapter 7 presents some design principles of vertical direct expansion ground-source heat pump systems. The main results from three representative case studies are finally summarized.

Chapter 8 first presents a number of design principles, including some of the thermal operating limits of closed-loop vertical thermo-syphon ground-source heat pump systems. Second, results from four case studies are summarized.

Chapter 9 presents the basic principle and main components of municipal water distribution systems as well as those of geothermal heat pump-based systems using municipal water as heat and sink sources for building heating and cooling processes. The most relevant benefits and limitations of such an un-conventional concept, and some findings from two case studies are also summarized.

Chapter 10 summarizes the municipal wastewater qualities, then provides some of design principles for municipal sewage-based ground-source heat pump systems. Finally, the advantages and limitations of such a non-conventional building and cooling concept are identified.

Chapter 11 first presents the basic configurations, construction principles, and some aspects of heat transfer for the proper design of building energy foundation-based ground-source heat pump systems for small- and large-scale buildings. Potential benefits and limitations of such non-conventional concepts are then identified. Finally, the leading results from three representative case studies are summarized.

Chapter 12 first presents some notions related to solar radiation, describes the main types of solar passive thermal collectors, a number of basic configurations and control strategies, and design principles for solar-assisted ground-source heat pump system. Second, a number of advantages and potential limitations of this technology are summarized. Finally, the concepts and main results from four cases studies are succinctly described.

Chapter 13 first presents the general physical conditions of roads, pavements, and bridges, and heat transfer characteristics aimed at melting snow and ice in cold and moderate climates. Second, the most common conventional non-thermal and thermal snow/ice melting methods and the ground-source heat pump-based snow/ice melting technology are succinctly described. Finally, some of the benefits and limitations of ground-source heat-pump-based snow/ice melting technology, as well as the leading results from two case studies, are summarized.

Chapter 14 first defines a number of terms currently used for low-energy buildings and succinctly describes some technologies employed in modern low-energy buildings. The main advantages and technological limitations of ground-source heat pump systems integrated in low-energy buildings are then identified. Finally, three case studies are presented.

Chapter 15 presents some important characteristics of mine waters as well as two basic configurations of open- and closed-loop concepts of ground-source heat pump systems using mine water as a heat source and sink for building space heating and cooling. Finally, the potential benefits and limitations of such non-conventional applications, and present and future opportunities, are identified.

Chapter 16 first presents the conventional district heating and cooling systems as well as some of their benefits and limitations. Second, reverse-return and circular concepts for low-temperature ground-source heat-pump-assisted district heating and cooling networks are described. Third, the main characteristics and leading results of three case studies are summarized.

Chapter 17 provides an overview of hybrid ground-source heat pump systems, including a short description of technology for both heating- and cooling-dominated commercial/institutional buildings, some design principles, and main advantage and limitations of potential applications. Finally, the result of four case studies are summarized.

2 Vertical Closed-Loop (Indirect, Secondary Fluid) Ground-Source Heat Pump Systems

DOI: 10.1201/9780367466589-2

2.1 Introduction

The design of vertical ground-coupled heat exchangers is complicated by the variety of geological formations and their thermophysical properties that usually can be estimated by using data for particular groups of ground/soils characteristic of local conditions. This method could be appropriate for residential and light commercial systems, but for systems with large annual differences between the amount of heat extracted (heating mode) and the amount rejected (cooling mode), some permanent change in the local ground temperature may be expected.

2.2 Design Principles and Steps

2.2.1 Types of Vertical Ground-Coupled Heat Exchangers

If large enough land areas are not available due to property boundaries or nearby structures, the ground-coupled heat exchangers should be placed vertically in the ground/soil/rocks, a configuration that allows greater depths to where the earth temperatures are higher and more stable in time.

One common method of installing vertical ground-coupled heat exchangers is to embed one (Figure 2.1) or two (Figure 2.2a) U-shaped pipes connected at the bottom, or coaxial (concentric) pipes (consisting of one central straight and another peripheral pipe with a large diameter) (Figure 2.2b) within drilled boreholes to carry a heat carrier fluid for heat extraction (in the winter) and heat injection (in the summer) (Mei and Fisher 1983; Bose et al. 1985; Acuna and Palm 2011). By using double U-tubes (Figure 2.2a) instead of single U-tubes in borehole heat exchangers, the heat dissipation capacity may increase by over 50% (Chen et al. 2010), which could justify the cost increase in installation and pumping energy consumption. However, a drawback of using double U-tubes may result in about a 20% reduction in temperature difference of thermal carrier fluid. In concentric tubes, which generally have larger diameters requiring larger liquid volume, the heat exchange with the surrounding earth occurs in the annular flow region. Some thermal “short-circuiting” occurs between the inner and outer flow channels, but this can be reduced with the use of low thermal conductivity inner pipes. In these systems, the heat carrier medium (generally, an antifreeze fluid called brine) is not in direct contact with the surrounding ground/soil/rock.

Figure 2.1 Vertical U-tube ground-coupled heat exchangers connected in: (a) series; (b) parallel reverse-return.

(Notes: schematics not to scale; not all components shown).

Figure 2.2 Vertical ground-coupled heat exchangers with: (a) double U-tubes; (b) concentric tubes.

(Notes: schematics not to scale; not all components shown).

Boreholes are drilled into the ground/soil/rocks deep enough to achieve adequate brine temperatures throughout the year depending on the heating- or cooling-dominated operating regime. The pipes are placed in the boreholes, and special distance brackets are used to separate the downward and upward tubes, in order to minimize the heat transfer between the tubes. After the tubes’ placement, the interior space is commonly filled with thermally conductive grout materials in order to enhance the heat transfer from the surrounding ground/soil/rocks and prevents the surface water from draining into the borehole and contaminating the groundwater. If, depending on the ground/soil/rock composition and thermal properties (e.g., temperature and moisture content), two or more boreholes are required, they can be connected in series (with only one brine flow path, achieving variation in the heat transfer from one borehole to the next) (Figure 2.1a) or in parallel reverse-return fashion (with multiple brine flow paths and with more uniform heat transfer across all boreholes on the runout) (Figure 2.1a). Both connecting configurations must provide minimum pressure drops at the brine nominal operating flow rates. Parallel-piped vertical heat exchangers can utilize U-tubes with smaller diameters than series-piped ones, resulting in lower borehole drilling, piping, brine, and labor costs. Usually, in order to minimize the thermal interactions, boreholes are spaced apart between 3 and 5 m, depending on the ground/soil/rock properties and building thermal loads.

2.2.2 Borehole Field Configurations

The unsteady, transient heat transfer process inside and around the vertical underground ground-coupled heat exchangers is strongly affected by the layout of borehole field (i.e., borehole relative locations, and distances to building, any obstructions or buried services as electric cables, and septic systems). Depending on local ground/soil conditions, the availability of drilling equipment and boreholes’ depths, vertical borefields require much less land than horizontal trenches (in the range is of about 5–7 m² per kW of building nominal cooling load) at costs of between 257 and 371 US$ per kW of nominal cooling capacity.

In order to ensure adequate brine circulation and distribution, precautions as the following should be taken during the design (Kavanaugh and Rafferty 1997): (i) U-tubes and headers should have as low as possible pressure drops; (ii) laminar brine flow should not occur in U-tubes, except at part thermal loads; and (iii) isolation valves must be provided to permit independently flushing fro...

Inhaltsverzeichnis

• Cover
• Half Title
• Title Page
• Copyright Page
• Contents
• Preface – Volume 2
• Author Biography
• Chapter 1 Introduction
• Chapter 2 Vertical Closed-Loop (Indirect, Secondary Fluid) Ground-Source Heat Pump Systems
• Chapter 3 Horizontal Closed-Loop (Indirect, Secondary Fluid) Ground-Source Heat Pump Systems
• Chapter 4 Open-Loop Multi-Well Groundwater Heat Pump Systems
• Chapter 5 Open-Loop, Single Well (Standing-Column) Ground-Source Heat Pump Systems
• Chapter 6 Horizontal Closed-Loop Direct Expansion Ground-Source Heat Pump Systems
• Chapter 7 Vertical Direct Expansion Ground-Source Heat Pump Systems
• Chapter 8 Closed-Loop Vertical Thermo-Syphon Ground-Source Heat Pump Systems
• Chapter 9 Municipal Water–Based Ground-Source Heat Pump Systems
• Chapter 10 Municipal Sewage–Based Ground-Source Heat Pump Systems
• Chapter 11 Building Energy Foundation–Based Ground-Source Heat Pump Systems
• Chapter 12 Solar-Assisted Ground-Source Heat Pump Systems
• Chapter 13 Snow Melting Ground-Source Heat Pump Systems
• Chapter 14 Ground-Source Heat Pump Systems for Low-Energy Buildings
• Chapter 15 Mine Water Ground-Source Heat Pump Systems
• Chapter 16 District Heating and Cooling Geothermal Systems
• Chapter 17 Hybrid Ground-Source Heat Pump Systems
• Index