Heat-Pump Chiller Valving for Heat Recovery and Low Pressure Drop
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Solution Overview
Problem
Existing HVAC&R systems face limitations in providing efficient heating and cooling for secondary fluids like water or brine, particularly in large buildings, and are prone to refrigerant leakage, which poses environmental concerns, especially with flammable and toxic refrigerants.
Innovation Solution
A system with a refrigerant circuit that includes an evaporator, compressor, and condenser, along with an external heat exchanger and control valving to regulate refrigerant flow, allowing for various operating modes such as cooling, heat pump, and defrost, minimizing refrigerant presence inside buildings and optimizing heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a reversing valve is used to switch between cooling and heat pump modes, then heating and cooling functions are enabled, but pressure drops become very high
Solution Approach 1:
The system divides the refrigerant flow control into separate paths using two four-way valves instead of one reversing valve. This segmentation allows independent control of refrigerant flow to different heat exchangers, eliminating the high pressure drop associated with traditional reversing valves while maintaining heating and cooling mode switching capability.
2Productivity
If refrigerant piping is extended to serve large buildings, then cooling capacity is increased, but refrigerant leakage risk increases
Solution Approach 1:
The system extracts the heat rejection function from the building interior by placing a condenser outside the building. This allows the refrigerant circuit to be shortened and confined to essential components only, minimizing refrigerant piping within the building while maintaining adequate cooling capacity for large spaces.
Solution Approach 2:
An external condenser acts as an intermediary between the refrigerant circuit and the building environment. This external component handles heat rejection outside the building, allowing the refrigerant system to operate with minimal internal piping and reduced leakage risk while still serving large building areas.
3Use of energy by moving object
If water-to-water heat pumps are used for simultaneous heating and cooling, then efficiency is improved, but system complexity increases
Solution Approach 1:
The system uses universal four-way valves that can direct refrigerant flow to multiple different heat exchangers (chillers, heat pumps, condensers) depending on operational mode. This multi-functionality allows a single valve assembly to replace what would otherwise require multiple dedicated components, reducing overall system complexity while maintaining the ability to perform simultaneous heating and cooling with high efficiency.
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 offers versatile operation, high energy efficiency, reduced refrigerant leakage, and lower costs by minimizing refrigerant piping and valve pressure drops, enabling simultaneous heating and cooling with controlled water temperatures and reduced environmental impact.
Implementation Method 1
an evaporator configured to vaporize a refrigerant to cool a first fluid stream
Implementation Method 2
a compressor coupled to the evaporator and configured to compress the vaporized refrigerant
Implementation Method 3
a condenser configured to condense the refrigerant compressed by the compressor to heat a second fluid stream
Implementation Method 4
Another heat exchanger, which may be positioned outside of a controlled space, such as a building, is configured to receive the refrigerant from the condenser, to selectively extract heat from or to add heat to the refrigerant
Data Source
AI summary
A heating and cooling system includes an evaporator, a compressor, and a condenser. A heat exchanger, which may be an outdoor heat exchanger, is configured to receive the refrigerant from the condenser, to selectively extract heat from or to add heat to the refrigerant, and to transfer the refrigerant to the evaporator. First control valving, disposed between the condenser and the heat exchanger, is configured to regulate flow of the refrigerant from the condenser to the heat exchanger in a first mode of operation. Second control valving, disposed between the condenser and the heat exchanger, is configured to regulate flow of the refrigerant from the heat exchanger to the evaporator in a second mode of operation. The system may be operated in a variety of modes by appropriate control of the valving and other system components.