PUMP-UP Module I PDF

1 INTRODUCTION 1.1 Lesson 1. Introduction to Heat Pumps and types. Heat pump technologies represent a highly efficient and versatile solution for heating and cooling buildings. These systems work by transferring heat from one location to another, rather than generating heat directly,...

1 INTRODUCTION 1.1 Lesson 1. Introduction to Heat Pumps and types. Heat pump technologies represent a highly efficient and versatile solution for heating and cooling buildings. These systems work by transferring heat from one location to another, rather than generating heat directly, making them significantly more energy-efficient than traditional heating methods. Heat pumps can extract thermal energy from various sources, including the air, ground, or water, and can be used for both space heating and cooling, as well as water heating. The technology behind heat pumps is based on the second law of thermodynamics and utilizes a refrigeration cycle to move heat against its natural flow from cold to hot areas. With their ability to provide both heating and cooling, heat pumps are a key technology in the transition to more sustainable and energy- efficient solutions for residential, commercial, and industrial applications. 1.2 Lesson 2. Fundamental Working Principles of HP systems (the HP cycle) Heat pumps operate on several fundamental principles based on thermodynamics and heat transfer. At their core, heat pumps utilize the vapor-compression refrigeration cycle to move thermal energy from a low- temperature source to a high-temperature sink. This process relies on the behavior of a refrigerant as it changes phases between liquid and gas states. The cycle consists of four main components: an evaporator, a compressor, a condenser, and an expansion valve. As the refrigerant circulates through these components, it absorbs heat from the source, is compressed to raise its temperature, releases heat to the sink, and then expands to lower its pressure and temperature. The efficiency of a heat pump is measured by its coefficient of performance (COP), which is the ratio of heat transferred to work input. Importantly, heat pumps can operate in reverse mode, allowing them to provide both heating and cooling functions. This versatility, combined with their ability to extract heat from various sources such as air, ground, or water, makes heat pumps a highly efficient and flexible technology for thermal management in buildings and industrial processes. 1.3 Lesson 3. Principles of HP selection and System Design Heat pump selection and design principles are essential to ensure optimum performance, energy efficiency and long-term comfort. The process begins with an accurate calculation of the heating and cooling loads of the space, considering factors such as size, insulation levels, local climate and heat sources. Unproper sizing with undersized units will struggle to meet demand, while oversized units will lead to inefficiency. Selection should consider the available heat source (air, ground or water) and climate considerations. Energy efficiency ratings such as Seasonal Energy Efficiency Ratio (SEER) for cooling and Heating Seasonal Performance Factor (HSPF) for heating should be analysed. In addition, the design should consider the [Título TFG] [Nombre y Apellidos] characteristics of the building, the heat distribution system and the potential for zoning. TFG Pág. 2 de 17 [Título TFG] [Nombre y Apellidos] 2 LECTURE NOTES 2.1 Lesson 1. Introduction to Heat Pumps and types. Heat pump technologies encompass a range of systems that transfer heat from one location to another for heating, cooling, and water heating purposes. Here are the main types of heat pump technologies: 2.1.1 Air-Source Heat Pumps (ASHPs) Most common type of heat pumps, Air-Source Heat Pumps (ASHPs) are highly efficient heating and cooling systems that extract heat from the outside air and transfer it indoors, or vice versa for cooling. These versatile devices operate on the principle of vapor compression, using a refrigerant to absorb and release heat as it cycles through the system. ASHPs typically achieve a Coefficient of Performance (COP) between 3 and 4, meaning they can produce 3 to 4 units of heat for every unit of electricity consumed. This high efficiency makes them an attractive option for reducing energy costs and carbon emissions in residential and commercial buildings. ASHPs are particularly effective in moderate climates but can also function in colder temperatures, with some models designed specifically for cold climates. As of 2023, ASHPs account for about 10% of building heating worldwide and are considered a key technology in phasing out gas boilers to reduce greenhouse gas emissions. Two main subtypes:  Air-to-air: Transfer heat between indoor and outdoor air.  Air-to-water: Heat water for radiators or underfloor heating. Figura 1. Air-Source Heat Pumps (ASHPs) TFG Pág. 3 de 17 [Título TFG] [Nombre y Apellidos] 2.1.2 Ground-Source Heat Pumps (GSHPs) Ground-Source Heat Pumps (GSHPs), also known as geothermal heat pumps, are highly efficient heating and cooling systems that utilize the relatively constant temperature of the earth to transfer heat. These systems consist of a heat pump unit connected to a series of underground pipes filled with a heat-transfer fluid. GSHPs can achieve higher efficiency ratings compared to air-source heat pumps, with coefficients of performance (COP) typically ranging from 3 to 6. This means they can produce 3 to 6 units of heat for every unit of electricity consumed. GSHPs are versatile, providing both heating and cooling for buildings, and can be used in various applications, from residential homes to large commercial structures. While they have higher upfront installation costs due to the need for ground excavation or drilling, GSHPs offer significant long-term energy savings and reduced carbon emissions, making them an attractive option for sustainable building design. 2.1.3 Water-Source Heat Pumps Water-Source Heat Pumps (WSHPs) are highly efficient heating and cooling systems that extract thermal energy from water bodies such as lakes, rivers, or groundwater aquifers. These systems typically consist of a heat pump unit connected to a network of submerged pipes or a direct water intake. WSHPs can achieve higher efficiency ratings compared to air- source heat pumps, with coefficients of performance (COP) often ranging from 3 to 5, meaning they can produce 3 to 5 units of heat for every unit of electricity consumed. The relatively stable temperature of water sources throughout the year allows for consistent performance in both heating and cooling modes. WSHPs can be designed as either closed-loop systems, where a heat transfer fluid circulates through submerged pipes, or open- loop systems, which directly use the water source. While installation costs can be higher due to the need for water access and specialized equipment, WSHPs offer significant long-term energy savings and reduced carbon emissions, making them an attractive option for buildings located near suitable water sources. 2.1.4 Absorption Heat Pumps Absorption Heat Pumps are thermally-driven systems that use heat as their primary energy source instead of electricity. These pumps typically employ a refrigerant-absorbent pair, such as ammonia-water or lithium bromide-water, to facilitate the heat transfer process. Unlike conventional electric heat pumps, absorption heat pumps use thermal energy to drive the refrigeration cycle, making them particularly suitable in applications where waste heat or low-cost thermal energy is available. They operate on a TFG Pág. 4 de 17 [Título TFG] [Nombre y Apellidos] principle similar to vapor compression systems but replace the mechanical compressor with a thermal compressor consisting of an absorber, generator, and solution pump. Absorption heat pumps can achieve coefficients of performance (COP) ranging from 0,8 to 1,6 for cooling and 1,2 to 2,5 for heating. While they typically have lower efficiency compared to electric heat pumps, absorption systems can be advantageous in situations where electricity is expensive or unavailable, or where there's an abundance of waste heat that can be utilized. Can be powered by natural gas, solar-heated water, or geothermal- heated water. Less common but useful in areas with limited electricity. 2.1.5 Advanced Technologies Recent innovations are significantly improving heat pump performance and efficiency. variable-speed compressors allow heat pumps to adjust their output to match heating or cooling demands more precisely, reducing energy waste. Advanced scroll compressors offer quieter operation and improved durability. The development of more environmentally friendly refrigerants, such as R-32, is enhancing efficiency while reducing environmental impact. Smart controls and Wi-Fi connectivity enable better system management and optimization based on usage patterns and weather forecasts. Some heat pumps now incorporate desuperheaters to recover waste heat for water heating. Cold climate heat pumps with enhanced vapor injection technology can maintain high efficiency even in sub-zero temperatures. These advancements are collectively pushing the boundaries of heat pump performance, with some systems achieving coefficients of performance (COP) above 5, meaning they produce more than five units of heat for every unit of electricity consumed. As a summary, several innovations are improving heat pump performance:  Variable-speed compressors: Allow for more efficient operation.  Scroll compressors: Quieter and more durable than traditional piston compressors.  Desuperheaters: Recover waste heat for water heating.  Improved refrigerants: Better performance and lower environmental impact. Heat pumps are considered a key technology for reducing carbon emissions from heating and cooling, due to their high efficiency and ability to use electricity from renewable sources. TFG Pág. 5 de 17 [Título TFG] [Nombre y Apellidos] 2.2 Lesson 2. Fundamental Working Principles of HP systems (the HP cycle). Heat pumps operate on the principle of heat transfer, utilizing a refrigerant to absorb heat from one location and release it in another. In heating mode, they extract heat from the outside air, even in cold conditions, and transfer it indoors. For cooling, the process is reversed, with heat being absorbed from inside the home and released outdoors. Figura 2. Figure 1. Heat Pump working principle 2.2.1 Components of Heat Pumps Heat pumps are complex systems composed of several key components working in tandem to provide efficient heating and cooling. The main components include:  Compressor: The core of the heat pump, pressurizing and circulating the refrigerant to facilitate heat transfer.  Evaporator: Absorbs heat from the environment, either from outside air (in heating mode) or indoor air (in cooling mode).  Condenser: Releases heat, expelling it outdoors in cooling mode or indoors in heating mode.  Expansion Valve: Regulates refrigerant flow and pressure, preparing it for heat absorption in the evaporator coil.  Reversing Valve: Enables switching between heating and cooling modes by reversing refrigerant flow. TFG Pág. 6 de 17 [Título TFG] [Nombre y Apellidos]  Refrigerant: The substance circulating through the system, changing states to absorb and release heat.  Fans: Present in both indoor and outdoor units, moving air over coils to facilitate heat exchange.  Indoor Unit (Air Handler): Houses the indoor coil and fan for distributing conditioned air.  Outdoor Unit: Contains the compressor, outdoor coil, and fans for heat exchange with the surrounding air.  Control Board: Manages overall system operations and ensures efficient performance. 2.2.1.1 Compressor The compressor has the function of raising the pressure of the refrigerant vapour from the suction pressure to the highest discharge pressure. In short, the compressor's mission is to suck in the gas that comes from the evaporator and transport it to the condenser by increasing its pressure and temperature. Upon entering the compressor, the fluid is in a gaseous state with low temperature and pressure. In the compressor, the gas is compressed, decreasing its volume and increasing the pressure and temperature, so that at the exit, the fluid is in a gaseous state of high temperature and pressure, transporting the thermal load of the acclimatized medium and the compression energy. Compressors can be classified into two large groups: volumetric or positive displacement compressors and centrifugal compressors. However, as for the motor-compressor coupling, these can be classified into:  Hermetic: Both the motor and the compressor are within the same enclosure that is inaccessible, and they share a shaft, which allows greater recovery of the heat generated by the motor. This type of compressor is focused on small critical load equipment, as is the case of the system under study. TFG Pág. 7 de 17 [Título TFG] [Nombre y Apellidos] Figura 3. Hermetic compressor used in the Heat Pump studied  Semi-hermetic: Like the hermetic, the motor and the compressor share a shaft, however in this case the compressor is accessible, which allows the repair of its parts. In addition, part of the heat generated in the engine is recovered in the coolant fluid, so the performance is higher than that of open engines. Figura 4. Example of a Semi-Hermetic Compressor  Open: Motor and compressor are separate, they are independent. The axles are coupled in the assembly ensuring tightness in the passage of the axle. TFG Pág. 8 de 17 [Título TFG] [Nombre y Apellidos] Figura 5. Open Compressor Example 2.2.1.2 Heat Exchangers Heat exchangers are important elements in the efficiency of heat pumps. Small temperature differences can be decisive in the energy efficiency of the system. The case of the heat pump analyzed is no exception. One of its main characteristics is that it is a reversible system, so the system's heat exchangers act both as a condenser and as an evaporator depending on the operating regime in which they operate. Thus, in the summer cycle, the internal exchanger will act as an evaporator and the external exchanger as a condenser, and vice versa during the winter cycle. The condenser has the function of bringing the gases coming from the compressor into contact with a means to liquefy it. The air entering the condenser in a gaseous state of low temperature and pressure is heated and becomes a refrigerant in a liquid state, giving up all its energy to the condenser air, the sum of the energy it absorbed in the evaporator (thermal load of the medium) and that provided by the compressor. In the process, a fan is required to suck in the air from the outside, circulate it through the condenser and return it back to the outside, preventing its recirculation and sending the hot air into the atmosphere. The evaporator is the place in the installation where the heat exchange between the refrigerant and the medium to be cooled takes place. The evaporator inlet air, a mixture of return air and ventilation, is cooled, dehumidified and transformed from liquid to gaseous. To do this, it is necessary to use a fan that sucks the air from the mixture, passes it through the evaporator and sends it to the medium to acclimatize, producing the effect of cooling the air. Bearing in mind that the external exchanger is reversible, it should be noted that during the summer cycle, the evaporator sucks the air out of the fluid, cools it, dehumidifies it and releases it into the medium to be acclimatized. However, in winter, the evaporator breathes in the air from the outside, cools, dehumidifies, and returns it to the external environment. TFG Pág. 9 de 17 [Título TFG] [Nombre y Apellidos] Figura 6. External Heat Figura 7. Internal heat Exchanger exchanger 2.2.1.3 Expansion Devices By means of this type of device, isoenthalpy pressure is reduced from condensation to evaporation pressure. Its function is to convert the refrigerant from high to low pressure, feeding the evaporator with the refrigerant fluid. The system analysed has two expansion valves, which have a section that can be automatically varied so that superheating after evaporation remains constant and no liquid droplets enter the compressor. Figura 8. Expansion Valve TFG Pág. 10 de 17 [Título TFG] [Nombre y Apellidos] 2.2.1.4 4-way valve This type of valve has four connections connected to the suction and discharge of the compressor, the evaporator and the condenser, through which the circulation of the gas is modified according to the action of the coil. With the coil at rest, the compressor sucks the gases from the evaporator and compresses it to the condenser, and with the coil excited, the circuit is altered and the compressor draws in from the condenser and compresses onto the evaporator. Finally, disconnecting the coil returns the system to the normal circuit in its initial state. Figura 9. 4-way valve 2.2.1.5 Deposits The system analyzed also includes two tanks. One located after the condenser and before the compressor used to prevent the entry of impurities into it; and another located at the exit of the evaporator, used to accumulate the excess fluid. Figura 10. Tank- Figura 11. Reservoir for TFG Pág. 11 de 17 [Título TFG] [Nombre y Apellidos] Accumulator before the excess coolant compressor 2.2.2 Working Modes 2.2.2.1 Winter Mode In winter, the heat pump operates by circulating refrigerant to transfer heat from the outside air to the interior of the building. The process begins with very cold, low-pressure refrigerant absorbing heat from the outdoor air in the external heat exchanger, even when temperatures are below freezing. This refrigerant then flows to the air-source heat pump's compressor, where it is mechanically pressurized, causing it to heat up significantly. A reversing valve directs this hot refrigerant to an indoor heat exchanger, where it transfers its heat to the indoor air. As the refrigerant cools, it passes through an expansion device, which makes it very cold again. Now colder than the outdoor temperature, the refrigerant can once more absorb heat from the outside air, restarting the cycle. This continuous process efficiently extracts heat from the outdoor environment and transfers it indoors, providing warmth even in cold weather conditions. Figure 2. Principle of Operation in Cooling Mode of the Heat Pump TFG Pág. 12 de 17 [Título TFG] [Nombre y Apellidos] 2.2.2.2 Heating Mode In summer, the heat pump process is reversed for cooling. The refrigerant passes through an expansion device, becoming very cold. This cold refrigerant then absorbs heat from the indoor air as it flows through the indoor heat exchanger, effectively cooling the interior space. The now- warmed refrigerant is compressed, further increasing its temperature and pressure. A reversing valve then directs this hot refrigerant to the outdoor heat exchanger. Here, since the refrigerant is hotter than the outside air, it releases its heat to the environment. This cycle operates similarly to a conventional air conditioning system, efficiently transferring heat from inside the building to the outside, thereby cooling the indoor space. https://goclean.masscec.com/article/how-air-source-heat-pumps- work/#tab-id-1 Figure 3. Principle of Operation in Heating Mode of the Heat Pump 2.3 Lesson 3. Principles of HP selection and System Design. Heat pumps are versatile climate control systems that operate differently depending on the environmental conditions, adapting to provide efficient heating or cooling across various climatic zones. Their performance and efficiency are significantly influenced by the ambient temperature and humidity levels, leading to distinct operational characteristics in different climate types. TFG Pág. 13 de 17 [Título TFG] [Nombre y Apellidos] In moderate climates: Heat pumps demonstrate superior efficiency, particularly when outdoor temperatures remain above 5-7°C (41-45°F). They can achieve substantial energy savings, potentially reducing consumption by 30-40% compared to traditional heating and cooling systems. The moderate temperature range allows for optimal heat exchange, maximizing the coefficient of performance (COP). These climates often experience balanced heating and cooling needs, allowing year-round utilization of the heat pump's capabilities. In warm climates: Heat pumps primarily function as air conditioners during summer months, extracting heat from inside the home and releasing it outdoors. They exhibit particularly high efficiency in regions characterized by mild winters and hot summers, where temperatures typically range between 0 and 35°C (32-95°F). The cooling mode operation is highly effective, as the temperature differential between indoor and outdoor environments facilitates efficient heat transfer. In these climates, heat pumps often provide an energy-efficient alternative to traditional air conditioning systems. In cold climates: The efficiency of heat pumps tends to decrease as outdoor temperatures drop below 0°C (32°F). When temperatures plummet below -20°C (-4°F), maintaining efficient operation becomes increasingly challenging. In very cold regions, heat pumps may require supplementary heating systems or the installation of more powerful, cold-climate-specific heat pump models. Advanced cold-climate heat pumps utilize enhanced technology to maintain efficiency at lower temperatures, such as variable-speed compressors and improved defrost cycles. General operation: TFG Pág. 14 de 17 [Título TFG] [Nombre y Apellidos] Heat pumps utilize a reversible refrigeration cycle to transfer heat between the interior and exterior of a building. In heating mode, they extract heat from the outside air, ground, or water source, and transfer it indoors. When cooling is required, the process is reversed, with heat being extracted from inside the building and released outside. The system comprises key components such as the compressor, condenser, expansion valve, and evaporator, which work in tandem to facilitate the heat transfer process. The efficiency of heat pumps is typically measured by the Coefficient of Performance (COP) for heating and the Energy Efficiency Ratio (EER) for cooling. These metrics are directly influenced by the ambient temperature, with performance generally improving as the temperature difference between the heat source and heat sink decreases. Thus, while heat pumps demonstrate optimal efficiency in moderate climates, technological advancements have expanded their effective operational range. However, in extreme climates, particularly very cold regions, they may require adaptations or complementary systems to maintain efficiency and meet heating demands. The selection and design of a heat pump system should always consider the specific climatic conditions of the installation site to ensure optimal performance and energy efficiency. Furthermore, Heat Pump selection and design is based on several key factors to ensure optimal performance, energy efficiency, and long-term comfort. The primary considerations include:  Heating and cooling load calculation: Determine the required capacity in British Thermal Units (BTUs) based on the space size, insulation levels, local climate, and heat sources.  Climate considerations: Select a heat pump suitable for the local climate, with higher Heating Seasonal Performance Factor (HSPF) ratings for colder regions.  Energy efficiency ratings: Look for high Seasonal Energy Efficiency Ratio (SEER) for cooling and HSPF for heating.  Heat source availability: Choose between air-source, ground-source (geothermal), or water-source heat pumps based on location, available space, and budget.  Building characteristics: Consider the building's insulation, airtightness, and existing heating system.  Heat distribution system: Design the distribution system (e.g., radiators, underfloor heating) to operate at low temperatures for increased efficiency. TFG Pág. 15 de 17 [Título TFG] [Nombre y Apellidos]  Proper sizing: Avoid oversizing or undersizing the heat pump, as both can lead to inefficiency and comfort issues.  Zoning considerations: Evaluate the need for zoned heating and cooling for more precise temperature control.  Brand and model selection: Research different brands and models, considering reliability, performance, and budget. Considering these factors, it can be selected and designed a heat pump system that provides efficient heating and cooling while minimizing energy consumption and environmental impact. TFG Pág. 16 de 17 [Título TFG] [Nombre y Apellidos] 3 BIBLIOGRAFÍA What are heat pumps and why are they important? | Climate Change Summit. https://climatechange-summit.org/ IEA (2022), *The Future of Heat Pumps*, IEA, Paris https://www.iea.org/reports/the-future-of-heat-pumps, Licence: CC BY 4.0. Gerring, D. (2024). Heat Pumps. In Renewable Energy Systems for Building Designers. Taylor & Francis. 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