Bi-Directional Cascade Heat Pump With Non-Mixing Fluid Loops
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Solution Overview
Problem
Current geothermal heat pump systems face limitations in operating modes, require reversible refrigerant circuits, and often mix high and low temperature fluids unnecessarily, necessitating a more versatile and efficient heat pump system for geothermal and conventional water source applications.
Innovation Solution
A heat pump system with multiple pumps and a secondary fluid source, where fluid flow is managed to avoid mixing high and low temperature fluids, allowing for various operating modes without reversing refrigerant flow or switching heat exchanger operations, and utilizing variable speed pumps to maintain desired temperature and heat transfer rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If reversible refrigerant circuits are used to provide multiple operating modes, then the system can achieve heating and cooling functions, but the system complexity increases due to the need for flow reversal mechanisms
Solution Approach 1:
The refrigerant system is divided into separate circuits: a first refrigerant circuit for heating mode and a second refrigerant circuit for cooling mode. Each circuit has its own compressor, condenser, and evaporator components, eliminating the need for complex flow reversal mechanisms while providing multiple operating modes.
Solution Approach 2:
The fluid circulation loop serves multiple functions by selectively connecting to different components of the first and second refrigerant circuits depending on the desired operating mode, providing both heating and cooling capabilities through a single multi-functional circulation system.
2Adaptability or versatility
If heat exchangers are switched between condensing and evaporating operations to achieve different modes, then the system can provide both heating and cooling, but the operational complexity increases
Solution Approach 1:
The heat exchanger system is segmented into dedicated components: first and second condensers for heating mode, and first and second evaporators for cooling mode. This segmentation eliminates the need to switch operations of the same heat exchanger, simplifying operational control.
3Ease of operation
If high and low temperature fluids are mixed to meet heating or cooling demands, then the system can simplify fluid management, but energy efficiency decreases due to unnecessary heat transfer
Solution Approach 1:
The fluid circulation system is segmented into separate flow paths: a first fluid circulation loop for heating mode and a second fluid circulation loop for cooling mode. This segmentation prevents mixing of high and low temperature fluids while maintaining simplified fluid management through selective valve control.
Solution Approach 2:
The fluid circulation loop acts as an intermediary system that selectively connects to different refrigerant circuits and heat exchangers based on operational demands, enabling temperature-appropriate fluid management without direct mixing of high and low temperature streams.
4Productivity
If multiple pumps are used to manage fluid flow between condensers and evaporators, then the system can optimize heat transfer, but the device complexity increases
Solution Approach 1:
The fluid circulation pump system is designed as a multi-functional unit that can selectively operate in different configurations: connecting condensers to evaporators for heat transfer optimization, or connecting to the geothermal fluid source for standard operation, reducing the need for multiple dedicated pumps.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides a wide range of heating and cooling modes with reduced fluid flow rates, minimizing unnecessary fluid mixing and enhancing operational efficiency by allowing fluid transfer between condensers and evaporators, thus optimizing heat transfer and meeting demand effectively.
Implementation Method 1
a condenser and an evaporator, wherein one of the condenser and the evaporator is in heat transfer relationship with the secondary fluid
Implementation Method 2
a refrigerant system that includes a compressor
Implementation Method 3
a first pump of variable speed connected in fluid communication with the geothermal fluid source and the fluid circulation loop
Data Source
AI summary
A multi-mode, bi-directional cascade heat pump system, according to some examples, includes at least two chillers each being part of a unidirectional refrigerant circuit. The system includes heat exchangers each of which are dedicated to operate as just a condenser or as just an evaporator, regardless of the system's operating mode. In some modes, a secondary fluid transfers heat between the condenser of one chiller and the evaporator of another chiller before the fluid returns to a secondary fluid source such as, for example, a geothermal borefield or a conventional water source. In some embodiments, fluid is withdrawn from a borefield by way of a pump having a speed that varies to maintain a desired fluid temperature and/or a desired heat transfer rate at the borefield. The heat pump system includes means for minimizing flow through the borefield and for minimizing unnecessary mixing of relatively high and low temperature fluid.