Air-conditioning apparatus including unit for increasing heating capacity
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Solution Overview
Problem
Existing air-conditioning apparatuses face challenges in maintaining heating capacity at low outdoor temperatures, particularly below -15 degrees C, due to low heat transfer efficiency and compressor operational issues, leading to reduced capacity and potential compressor protection problems.
Innovation Solution
An air-conditioning apparatus that incorporates an auxiliary heat exchanger using an external heat source, such as hot water from a boiler, to increase the refrigerant's evaporating temperature, thereby enhancing heating capacity and preventing compressor discharge temperature rise, while optimizing the use of both indoor and outdoor heat exchangers based on temperature conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gas refrigerant or two-phase refrigerant injection into compressor is used for heating under low outdoor temperature, then heating capacity is improved, but heating capacity ratio drops when outdoor temperature further decreases
Solution Approach 1:
An auxiliary heat exchanger is introduced as an intermediary component between the refrigerant circuit and the heating system. This heat exchanger receives refrigerant from the refrigerant circuit and exchanges heat with external heat source water, serving as a mediator that enhances heating capacity without directly modifying the compressor operation or refrigerant injection process.
Solution Approach 2:
The invention combines two heating sources: the refrigerant circulation system and an external heat source water system. By merging these two independent heating mechanisms through the auxiliary heat exchanger, the system achieves enhanced overall heating capacity that compensates for the drop in heating capacity ratio at low temperatures.
2Temperature
If outdoor air temperature drops below -15 degrees C, then evaporating temperature becomes low and compressor discharge temperature increases, but compressor protection is required hindering normal operation
Solution Approach 1:
The auxiliary heat exchanger acts as a thermal intermediary that allows heat transfer from external heat source water to the refrigerant without requiring the refrigerant to operate at extremely low evaporating temperatures. This mediator function enables the system to maintain reliable compressor operation even when outdoor temperatures drop below -15°C.
Solution Approach 2:
The system changes the operating parameters by introducing external heat source water with a higher temperature than the outdoor air. This parameter change allows the refrigerant to absorb heat at a more favorable temperature level, preventing excessive compressor discharge temperature rise while maintaining heating effectiveness.
3Power
If heat is exchanged between air heated by hot water of boiler and refrigerant through air heat exchanger, then heating operation is enabled, but heat transfer efficiency is low
Solution Approach 1:
Instead of directly exchanging heat between heated air and refrigerant through an air heat exchanger (which has low efficiency due to air's poor thermal conductivity), the invention uses water as an intermediary medium. The external heat source water absorbs heat from the boiler and transfers it to the refrigerant through the auxiliary heat exchanger, significantly improving heat transfer efficiency since water has much better thermal properties than air.
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 solution enables continuous heating operations at low outdoor temperatures by increasing refrigerant circulation and heating capacity, effectively utilizing the outdoor heat exchanger and reducing pressure losses, thus maintaining efficient heating performance.
Implementation Method 1
heat is added to the refrigerant by the external heat source in the auxiliary heat exchanger
Implementation Method 2
heat is added to the refrigerant by the external heat source in the auxiliary heat exchanger, the evaporating temperature of the refrigerant in the refrigeration cycle becomes high
Data Source
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AI summary
An air-conditioning apparatus including a check valve CV1 that is provided in a passage between a first flow switching device 3 and a suction side of a compressor 1, a liquid piping expansion valve LEV2 that is provided in midway of a liquid extension piping 20 and is capable of controlling a throughput of a refrigerant, an additional unit having a first bypass 22a and a second bypass 22b that are branched off from a passage between an indoor unit and the liquid expansion valve and are connected to a passage between the check valve and the suction side of the compressor, in which the first bypass has, in midway thereof, a first bypass expansion valve LEV1a capable of controlling a throughput of refrigerant and an auxiliary heat exchanger that has a heat source for heating different to the refrigerant, the auxiliary heat exchanger 24 functioning as an evaporator heating the refrigerant flowing in the first bypass and in which the second bypass has, in midway thereof, a second bypass expansion valve LEV1b capable of controlling a throughput of refrigerant.