Compressor Priority Control for Cooling and Hot Water Recovery
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Solution Overview
Problem
Combined air-conditioning and hot water supply systems face inefficiencies in simultaneous cooling and hot water supply operations, leading to prolonged hot water supply times and potential shortages, due to fixed compressor frequency settings and inadequate waste heat recovery.
Innovation Solution
A control system that dynamically adjusts the compressor frequency based on temperature differentials between set hot water supply temperatures and inlet water temperatures, switching between cooling priority and hot water supply priority modes to optimize waste heat recovery and maintain indoor comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the heating capacity is set to a large value to reduce hot water supply time, then hot water supply completion time is shortened, but the system operates in a low-efficiency state
Solution Approach 1:
The patent applies dynamics by making the heating capacity variable rather than fixed. The control device dynamically adjusts the heating capacity based on the temperature differential between inlet water and set hot water supply temperature. When the temperature differential is large, the heating capacity is increased to shorten supply time; when the temperature differential is small, the heating capacity is reduced to maintain high operating efficiency. This resolves the contradiction between speed and energy efficiency.
2Device complexity
If the compressor operating frequency is controlled to a fixed value when cooling load is small, then the system operates simply, but the operating efficiency becomes low
Solution Approach 1:
The patent implements dynamic control of compressor operating frequency based on cooling load conditions. When cooling load is small, the compressor frequency is controlled to a fixed value for simple operation; when cooling load is large, the frequency is adjusted according to the cooling load to maintain high efficiency. This dynamic adaptation resolves the contradiction between control simplicity and energy efficiency.
Solution Approach 2:
The patent changes the operating parameters (compressor frequency and heating capacity) based on operating conditions. By monitoring cooling load and temperature differential, the system adjusts these parameters to optimize efficiency across different operating scenarios, resolving the contradiction between fixed simple control and efficient variable operation.
3Reliability
If the cooling capacity is set to match the total cooling load, then indoor comfort is maintained, but waste heat recovery for hot water supply becomes insufficient
Solution Approach 1:
The patent applies dynamics by enabling the system to operate in different modes (cooling priority mode and hot water supply priority mode) based on temperature differential. In cooling priority mode, cooling capacity matches cooling load for comfort; in hot water supply priority mode, the system adjusts to provide sufficient waste heat for hot water supply. This dynamic mode switching resolves the contradiction between comfort and heat recovery quantity.
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 efficiently recovers waste heat for hot water supply, preventing prolonged completion times and shortages, while maintaining indoor comfort by dynamically controlling compressor frequency according to operational needs.
Implementation Method 1
a compressor (1) that compresses the refrigerant
Implementation Method 2
an outdoor side heat exchanger (3) that heats or cools outdoor air
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A combined air-conditioning and hot water supply system for simultaneously executing a cooling operation and a hot water supply operation is provided, in which the operation of a compressor is controlled to complete hot water supply with high efficiency and in a short time to thereby prevent running out of hot water. In a case where a combined air-conditioning and hot water supply system 100 simultaneously executes the cooling operation of a use unit 303 and the hot water supply operation of a hot water supply unit 304, the combined air-conditioning and hot water supply system 100 operates in a cooling priority mode when the temperature differential ΔTwm between a set hot water supply temperature Twset and the inlet water temperature Twi of a plate water-heat exchanger 16 is smaller than a priority operation determination threshold M that is set in advance, and operates in a hot water supply priority mode when the temperature differential ΔTwm becomes equal to or higher than the priority operation determination threshold M. In the cooling priority mode, the operating frequency of a compressor 1 is controlled in accordance with the temperature differential between the suction air temperature of the use unit 303 and the indoor set temperature of the use unit 303. In the hot water supply priority mode, the operating frequency of the compressor 1 is controlled in accordance with the temperature differential between the set hot water supply temperature Twset and the water temperature in a hot water supply tank 305.