Heat Pump Circulation Control for Low-Load Heating Stability

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Solution Overview

Problem

The existing heat medium circulation systems often increase the frequency of start and stop for heating means, leading to reduced lifespan due to higher heat medium temperatures being supplied to indoor-heating terminals, compromising comfort and efficiency.

Innovation Solution

A heat medium circulation system that includes a heat pump device, flow rate sensor, outlet temperature sensor, return temperature sensor, and a controller to adjust the heating power and circulation flow rate, ensuring the heat medium temperature remains within the desired range, thereby reducing unnecessary start and stop cycles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of moving object

If the heat pump is operated with minimum heating power and the heat medium temperature is increased to delay stop timing, then the start and stop frequencies are reduced, but the temperature supplied to the indoor-heating terminal becomes higher than desired, impairing comfortability

Engineering Contradiction:
Improveoperation duration of heat pumpVSAvoidheat medium temperature
Core Design Contradiction:
Duration of action of moving objectVSTemperature

Solution Approach 1:

The system dynamically changes the circulation flow rate parameter based on operating conditions. When the heat pump operates at minimum heating power, the circulation flow rate is increased to maintain the heat medium temperature within the desired range while still delaying the stop timing, thus reducing start-stop frequencies without compromising comfortability

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The circulation flow rate is made dynamic rather than fixed. The control device adjusts the circulation flow rate in real-time based on the heat pump's operating state, allowing the system to adapt to varying heating demands and maintain optimal temperature levels while extending operation duration

Inventive Principle:
Principle #15Dynamics

2Temperature

If the circulation flow rate is increased to maintain lower heat medium temperature, then comfortability is improved, but energy consumption of the circulation pump increases

Engineering Contradiction:
Improveheat medium temperatureVSAvoidenergy consumption of circulation pump
Core Design Contradiction:
TemperatureVSUse of energy by moving object

Solution Approach 1:

The system optimizes the circulation flow rate parameter by calculating the minimum required flow rate based on the heat pump's heating power and the desired temperature difference. This ensures the circulation pump consumes only the necessary energy to maintain comfortability, avoiding excessive energy consumption while still achieving the temperature control objective

Inventive Principle:
Principle #35Parameter changes

3Use of energy by moving object

If the heat pump operates frequently to match low indoor-heating load, then energy efficiency is improved, but the life of the heating means is shortened due to increased start and stop frequencies

Engineering Contradiction:
Improveenergy efficiencyVSAvoidlife of heating means
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The system maintains continuous operation of the heat pump by adjusting the circulation flow rate rather than frequently stopping and starting the heating means. By increasing the circulation flow rate to manage temperature when operating at minimum heating power, the heat pump can run continuously or for extended periods, preserving its lifespan while still matching the low indoor-heating load efficiently

Inventive Principle:
Principle #20Continuity of useful action

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 system effectively reduces the frequency of heating means start and stop cycles without exceeding desired heat medium temperatures, enhancing comfort and extending the lifespan of heating components.

Implementation Method 1

a heat pump device 11 that heats a heat medium

Methodology Applied
Scientific EffectHeat pump heating: Heat Exchanger

Implementation Method 2

a pump device 2 that circulates the heat medium

Methodology Applied
Scientific EffectPumping: Pump

Data Source

PatentEP3604933B1Heat medium circulation system
Publication Date: 2023.03.08 MITSUBISHI ELECTRIC CORP
  • EP3604933B1 patent drawingFigure 1
  • EP3604933B1 patent drawingFigure 2
  • EP3604933B1 patent drawingFigure 3

AI summary

A heat medium circulation system (1) includes a heat pump device (11) that heats a heat medium, a pump (2) that circulates the heat medium in a circulation circuit passing through an indoor-heating terminal (20) and the heat pump device (11), load detection means that detects an indoor-heating load during an indoor-heating operation in which the heat medium heated by the heat pump device (11) is supplied to the indoor-heating terminal (20), and a controller (6) that adjusts a heating power of the heat pump device (11) and a circulation flow rate that is a flow rate of the heat medium passing through the heat pump device (11). In the case where the indoor-heating load detected when the circulation flow rate is equal to a first flow rate is lower than a minimum load that is a load balanced with a minimum heating power of the heat pump device (11), the controller (6) adjusts the circulation flow rate such that the circulation flow rate is higher than the first flow rate.