Cascade Heat Pump Layout for Multi-Mode Geothermal Operation
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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 fluid circulation loop that allows for variable speed operation and selective configuration of heating and cooling modes, avoiding the need for refrigerant flow reversal and heat exchanger operation switching, by using a secondary fluid source with temperature sensors to control fluid flow and heat transfer between a condenser and evaporator.
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 system divides the refrigerant circuit into separate heating circuit and cooling circuit, each with dedicated evaporators and condensers. This segmentation eliminates the need for reversible components while providing multiple operating modes through independent circuit operation.
Solution Approach 2:
The fluid circulation loop serves multiple functions by selectively connecting to different heat exchangers (evaporators and condensers) depending on the desired operating mode. The same loop can provide heating, cooling, or both simultaneously by adjusting valve configurations.
2Adaptability or versatility
If heat exchangers are switched between condensing and evaporating operation to provide different modes, then the system achieves operational flexibility, but the system requires complex switching mechanisms
Solution Approach 1:
Each heat exchanger is designed with dedicated heating and cooling components rather than requiring single heat exchangers to switch functions. The heating circuit has its own evaporators and condensers, as does the cooling circuit, eliminating the need for operational switching.
Solution Approach 2:
The system uses dynamic valve control to selectively connect different heat exchangers to the fluid circulation loop based on operational requirements. This dynamic configuration allows the system to provide heating, cooling, or combined modes without physically switching heat exchanger functions.
3Device complexity
If high and low temperature fluids are mixed to simplify system design, then the system structure becomes simpler, but energy efficiency decreases due to unnecessary heat exchange
Solution Approach 1:
The fluid circulation system is segmented into separate heating and cooling loops that operate independently. High temperature heating fluid and low temperature cooling fluid circulate through separate pathways, preventing unnecessary mixing while maintaining system simplicity through modular design.
Solution Approach 2:
The system uses intermediate heat exchangers and isolation valves as mediators between different temperature zones. This allows the system to maintain separate temperature zones without complex mixing prevention mechanisms, preserving energy efficiency while simplifying the overall structure.
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
Enables a wide range of heating and cooling modes with reduced fluid flow rates, minimizing unnecessary fluid mixing and enhancing operational flexibility and efficiency in geothermal and water source systems.
Implementation Method 1
a first chiller with a condenser, a second chiller with an evaporator, and a fluid circulation loop coupling the geothermal fluid source in heat transfer relationship with the first chiller and the second chiller
Implementation Method 2
a first pump of variable speed connected in fluid communication with the geothermal fluid source and the fluid circulation loop
Implementation Method 3
a first temperature sensor at a first location on the fluid circulation loop, and a second temperature sensor at a second location on 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.