Heat Pump Tank Charging with Staged Cold-Start Temperature Control
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Solution Overview
Problem
Conventional heat pump hot water supply apparatuses face challenges in efficiently accumulating heat, as low-temperature liquid often flows into the tank during the start of heat accumulating operations, leading to reduced heat accumulation and deterioration in coefficient of performance (COP).
Innovation Solution
A heat pump apparatus that divides the heat accumulating operation into stages, controlling the water flow rate and temperature setpoints to prevent low-temperature liquid from entering the tank, with a first stage having a lower target temperature than the second stage, optimizing water flow rates and temperatures to enhance heat transfer efficiency and reduce COP deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the heat accumulating operation starts immediately, then the operation continuity is improved, but low-temperature liquid flows into the tank causing heat accumulation efficiency to deteriorate
Solution Approach 1:
The control device performs preliminary action by detecting the temperature of liquid discharged from the heat exchanger before it enters the tank. When the temperature is below the predetermined threshold, the control device stops the water pump in advance to prevent low-temperature liquid from flowing into the tank, thereby maintaining heat accumulation efficiency while enabling continuous operation.
Solution Approach 2:
The system implements feedback control by continuously monitoring the discharged liquid temperature and using this information to control the water pump operation. The control device adjusts the pump operation based on real-time temperature feedback, ensuring that only appropriately heated liquid enters the tank while maintaining operational continuity.
2Loss of energy
If the water pump is stopped to prevent low-temperature liquid from entering the tank, then heat accumulation efficiency is improved, but operational continuity deteriorates
Solution Approach 1:
The system changes the operational parameters dynamically by adjusting the water pump operation based on the discharged liquid temperature. When temperature exceeds the predetermined value, the pump operates; when it falls below, the pump stops. This parameter-based control resolves the contradiction by adapting the system operation to real-time thermal conditions.
3Manufacturing precision
If the circulating pump rotation speed is controlled to match set temperature, then hot water temperature precision is improved, but system complexity increases
Solution Approach 1:
The control device uses feedback from temperature sensors to adjust the circulating pump rotation speed. The temperature detection unit monitors hot water temperature, and the control device compares it with the set temperature to determine the appropriate pump speed, achieving precise temperature control through feedback-based adaptive control.
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 effectively prevents low-temperature liquid from entering the tank during both cold and hot starts, enhancing heat accumulation and maintaining a high coefficient of performance (COP) by optimizing water flow rates and temperatures across the heat accumulating stages.
Implementation Method 1
a heat exchanger between refrigerant and water in the hot water circuit
Implementation Method 2
a circulating pump in the hot water circuit
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
There is provided a heat pump apparatus capable of preventing a low-temperature liquid from flowing into a tank while reducing deterioration in COP at the start of heat accumulating operation. A heat pump apparatus includes: a compressor configured to compress refrigerant; a heat exchanger configured to exchange heat between the refrigerant compressed by the compressor and a liquid; a pump configured to pump the liquid; a tank; a controller configured to control heat accumulating operation in which the liquid heated in the heat exchanger is accumulated in the tank; and means for detecting or estimating compressor temperature that is temperature of the compressor or temperature of the refrigerant discharged from the compressor. The controller is configured to: determine whether a hot start or a cold start based on the compressor temperature at the start of the heat accumulating operation, and make, in case of the cold start, temperature of the liquid flowing out of the heat exchanger in a first stage of the heat accumulating operation lower than temperature of the liquid flowing out of the heat exchanger in a second stage of the heat accumulating operation.