Heat Pump Subcooling Control for Stable COP in Floor Heating
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Solution Overview
Problem
Heat pump type floor heaters experience inefficient operation due to the large variation in Coefficient of Performance (COP) caused by changes in supercooling degree, which is not as effectively controlled as in air conditioners, leading to potential efficiency deterioration.
Innovation Solution
A heat pump apparatus with a refrigerant circuit including a compressor, utilization-side heat exchanger, electronic expansion valve, and outdoor heat exchanger, along with a controller that adjusts the electronic expansion valve's opening degree based on calculated subcooling values derived from condensing pressure and compressor rotation number to maintain optimal subcooling conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the heat pump apparatus uses a conventional refrigerant circuit structure similar to air conditioners, then device complexity is reduced and ease of manufacture is improved, but the COP deteriorates due to large variation in supercooling degree
Solution Approach 1:
The patent applies parameter changes by introducing a new control parameter (subcooling degree) in addition to the existing evaporating temperature parameter. The controller now manages both evaporating temperature and subcooling degree independently, allowing precise adjustment of refrigerant state parameters to optimize heat exchange efficiency while maintaining the conventional refrigerant circuit structure.
2Loss of energy
If the SC value is strictly controlled in heat pump type floor heater, then the COP is improved, but device complexity increases compared to air conditioner control
Solution Approach 1:
The patent implements feedback control by using a subcooling degree calculator that continuously monitors refrigerant temperature and pressure to determine the actual subcooling degree. This calculated value is fed back to the controller, which then adjusts the electronic expansion valve to maintain the optimal subcooling degree, creating a closed-loop control system that automatically compensates for variations.
Solution Approach 2:
The patent replaces mechanical control mechanisms with electronic control. Instead of using mechanical throttling devices or complex mechanical control systems, the invention uses an electronic expansion valve controlled by electronic calculations of subcooling degree based on temperature and pressure sensor data, substituting mechanical complexity with electronic intelligence.
3Device complexity
If the electronic expansion valve opening degree is adjusted based on evaporating temperature only, then device complexity is kept simple, but the subcooling degree varies causing COP deterioration
Solution Approach 1:
The patent applies dynamics by making the control system adaptive and responsive to changing operating conditions. The subcooling degree calculator continuously updates the subcooling degree based on real-time temperature and pressure measurements, and the controller dynamically adjusts the electronic expansion valve opening degree accordingly, allowing the system to adapt to varying load conditions, ambient temperatures, and water flow rates.
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 enhances the operational efficiency of heat pump systems by delicately controlling subcooling according to various operation conditions, maintaining a high COP even under changing condensing pressures and compressor rotation numbers.
Implementation Method 1
a utilization-side heat exchanger (3) for exchanging heat between water and refrigerant
Implementation Method 2
the condenser is provided with a condensing temperature detector for detecting temperature of the refrigerant in the condenser
Implementation Method 3
an evaporator are sequentially connected by piping
Implementation Method 4
controls an opening degree of the electronic expansion valve so that the result of the calculation may reach an objective value
Implementation Method 5
a compressor, a condenser, an electronic expansion valve, and an evaporator are sequentially connected by piping
Data Source
AI summary
A heat pump apparatus includes: a refrigerant circuit which includes a compressor, a utilization-side heat exchanger for exchanging heat between water and refrigerant, an electronic expansion valve, and an outdoor heat exchanger; a controller which controls the compressor and the electronic expansion valve; a subcooling value calculating unit which calculates a subcooling value of the refrigerant circuit; a condensing pressure detector which detects condensing pressure of the compressor; a compressor rotation number detector which detects rotation number of the compressor; and an objective subcooling value extracting unit which selects and extracting an objective subcooling value stored in advance, from the condensing pressure and the rotation number of the compressor. The controller adjusts an opening degree of the electronic expansion valve so that the calculated subcooling value of the refrigerant circuit reaches the objective subcooling value.