Cycle system for heating and/or cooling and heating and/or cooling operation method
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Solution Overview
Problem
Air-to-water heat pumps become oversized and inefficient at low heat loads, leading to frequent cycling, reduced efficiency, and increased electricity costs, especially in well-insulated homes, due to the increase in refrigerant dryness at the evaporator inlet when using existing bypass circuit configurations.
Innovation Solution
A cycle system with a bypass passage connected between the compressor outlet and condenser inlet, and between the condenser outlet and evaporator inlet, incorporating an internal heat exchanger and additional expansion valves to manage refrigerant flow and prevent dryness, allowing continuous operation at low heat loads without cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a bypass circuit is used to enable partial heat load operation, then the heat pump can run continuously at low heat loads, but the refrigerant dryness at the evaporator inlet increases causing reduced heat transfer efficiency
Solution Approach 1:
A liquid receiver is introduced as an intermediary component between the bypass circuit and the evaporator. The liquid receiver stores excess refrigerant and ensures that only liquid refrigerant is supplied to the evaporator, preventing refrigerant dryness while maintaining continuous operation capability at partial heat loads.
Solution Approach 2:
The system changes the physical state parameter of the refrigerant by ensuring complete condensation in the liquid receiver before supply to the evaporator. This parameter change (from potential vapor-liquid mixture to confirmed liquid state) prevents evaporator dryness and maintains heat transfer efficiency during bypass operation.
2Use of energy by moving object
If the compressor runs at minimum frequency to match low heat load, then energy consumption is reduced, but the supply flow temperature rises above the overheating threshold causing frequent cycling
Solution Approach 1:
The liquid receiver acts as a thermal buffer and intermediary that allows the compressor to run continuously at minimum frequency. By storing excess refrigerant and regulating flow to the evaporator, it prevents supply temperature from rising above the overheating threshold, ensuring operational stability while maintaining low energy consumption.
3Device complexity
If high-pressure hot gas is injected directly into the main circuit before the expansion valve, then the bypass circuit is simplified, but the refrigerant composition at the evaporator inlet has higher vapor fraction reducing heat exchange efficiency
Solution Approach 1:
The liquid receiver serves as an intermediary that reconciles the simple bypass circuit configuration with efficient heat exchange. It receives high-pressure hot gas from the bypass circuit, ensures complete condensation, and supplies pure liquid refrigerant to the evaporator, maintaining heat exchange efficiency without complicating the bypass circuit design.
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 maintains heat transfer efficiency by condensing hot gas in the bypass passage, reducing compressor on-off cycling and preventing refrigerant dryness, thus ensuring continuous operation and improved energy efficiency at low heat loads.
Implementation Method 1
the bypass passage includes an internal heat exchanger for exchanging heat between the first refrigerant part and a second refrigerant part
Data Source
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AI summary
The present invention relates to a cycle system for heating and/or cooling comprising a main circuit for circulating a refrigerant having a compressor, a condenser, a first expansion valve and an evaporator, which are sequentially connected in a flow direction of the refrigerant, and a bypass passage for bypassing a first refrigerant part around the condenser, wherein the bypass passage includes an internal heat exchanger for exchanging heat between the first refrigerant part and a second refrigerant part which is branched off from the main circuit at the evaporator outlet, and the main circuit further comprises a liquid receiver, which is connected to the bypass passage.