Heat Pump Compressor Oil Temperature Control for Low-GWP Refrigerants
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Solution Overview
Problem
Heat pumps using low environmental impact refrigerants face challenges with compressor delivery temperatures that can exceed safe limits, leading to overheating and lubrication issues, which compromise mechanical components and reduce operating ranges compared to traditional refrigerants.
Innovation Solution
A management logic for heat pumps that regulates the wet fraction of the refrigerant at the compressor inlet by adjusting the evaporator's power to maintain a temperature difference between the lubricating oil and the refrigerant, ensuring the lubricating oil remains above a safety threshold, thereby preventing condensation and maintaining optimal compressor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If low GWP refrigerants are used, then environmental impact is reduced, but compressor delivery temperature increases causing overheating and lubrication issues
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the evaporator power level (high, medium, low) based on operating conditions such as delivery temperature, suction temperature, and temperature differential. This controls the refrigerant state parameters (temperature, pressure, humidity fraction) entering the compressor to maintain delivery temperature within safe limits while using low GWP refrigerants
Solution Approach 2:
The patent implements a feedback control system that continuously monitors delivery temperature, suction temperature, and temperature differential, then adjusts evaporator power accordingly. The control logic modifies operating parameters based on measured values to maintain optimal compressor operation and prevent overheating
2Temperature
If evaporator power is increased to cool refrigerant, then delivery temperature decreases, but operating range and efficiency are compromised
Solution Approach 1:
The patent applies dynamics by making the evaporator power level adjustable and variable rather than fixed. The system dynamically switches between high, medium, and low power levels based on real-time operating conditions, allowing optimal adaptation to different environmental and load conditions while maintaining delivery temperature control
Solution Approach 2:
The control system changes operating parameters (evaporator power level, refrigerant flow rate) based on measured conditions to maintain optimal performance across different operating scenarios without compromising the operating range
3Reliability
If delivery temperature is reduced to prevent overheating, then compressor reliability improves, but operating efficiency decreases
Solution Approach 1:
The patent optimizes parameter combinations (temperature differential, suction temperature, delivery temperature) to maintain compressor reliability while maximizing efficiency. By controlling the humidity fraction and temperature parameters within optimal ranges, the system achieves both reliability and efficiency goals
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
This approach ensures the compressor operates within safe temperature limits, preventing overheating and lubrication issues while maintaining the operating range of the heat pump, even with low GWP refrigerants, thus enhancing reliability and efficiency.
Implementation Method 1
at least a first heat exchanger in which the operating fluid absorbs, at constant pressure, heat energy from a first fluid F.f
Implementation Method 2
a compressor actuated by a motor and designed to compress said operating fluid between a minimum pressure thereof, that it has at the outlet of the first exchanger, to the maximum pressure that it has at the inlet of the second exchanger
Implementation Method 3
at least a second heat exchanger, in which the same operating fluid yields, at constant pressure, part of its heat energy to a second fluid F.c
Implementation Method 4
a lamination valve that achieves an expansion, at substantially constant enthalpy, and a cooling of the operating fluid
Data Source
AI summary
A method for managing and controlling a heat pump based on a compression/expansion thermodynamic cycle of an operating fluid including at least: first and second heat exchangers; an expansion valve; and a compressor. The compressor is able to suck and compress a wet operating fluid. A plurality of temperature sensors detects the delivery temperatures Tm of the compressor, an evaporation temperature SST in the first exchanger, and a condensation temperature SDT in the second exchanger. The temperature difference between the lubricating oil in the compressor and the operating fluid at the compressor delivery is kept equal to or greater than a safety threshold OIL_SH such that there is no condensation of the operating fluid in the lubricating oil.