Branch Unit Pressure Control for Even Refrigerant Distribution
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Solution Overview
Problem
Conventional air-conditioning systems with a main branch unit and sub-branch units experience complex refrigerant pipe connections and crossover wiring, leading to increased refrigerant volume and pressure loss, complicating control and distribution.
Innovation Solution
A refrigeration cycle apparatus with only sub-branch units, featuring a heat source unit, branch units with intermediate heat exchangers and expansion devices, and a refrigerant circuit with high-pressure, low-pressure, and intermediate-pressure pipes, along with pressure detecting devices to control expansion devices for optimal refrigerant distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a main branch unit and sub-branch units are serially connected to supply refrigerant, then cooling and heating operations can be freely selected in each indoor unit, but the refrigerant pipes and control wiring become complicated and pressure loss increases
Solution Approach 1:
The system divides the refrigeration cycle apparatus into multiple independent branch units, each capable of autonomous operation. Each branch unit includes its own expansion device and intermediate heat exchanger, allowing independent control for cooling or heating operations without requiring complex serial connections through a main branch unit.
Solution Approach 2:
Each branch unit is designed to perform multiple functions - both cooling and heating operations can be executed by any branch unit independently. The intermediate heat exchanger can serve as either an evaporator or condenser depending on the operation mode, eliminating the need for dedicated main branch units and complex wiring.
2Adaptability or versatility
If main branch unit and sub-branch units are serially connected, then multi-air-conditioning operation is achieved, but the amount of enclosed refrigerant increases
Solution Approach 1:
By segmenting the system into parallel branch units rather than serial connections, the refrigerant path length is reduced. Each branch unit has direct access to the high-pressure and low-pressure refrigerant pipes, eliminating the need for extensive refrigerant distribution through a main branch unit and its sub-branches.
3Quantity of substance
If main branch unit and sub-branch units are serially connected, then refrigerant distribution is achieved, but pressure loss increases disadvantageously
Solution Approach 1:
The refrigerant distribution system is segmented into independent parallel branches rather than a single serial path. Each branch unit connects directly to the high-pressure and low-pressure pipes, significantly reducing the total refrigerant path length and minimizing pressure loss compared to serial connections through a main branch unit.
Solution Approach 2:
The system transitions from a one-dimensional serial connection (main branch → sub-branches) to a two-dimensional parallel architecture (multiple independent branches). This dimensional change allows refrigerant to reach all indoor units through shorter, more direct paths, reducing cumulative pressure loss.
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 configuration simplifies refrigerant pipe and control wiring, reduces enclosed refrigerant volume, and minimizes pressure loss, enabling efficient cooling and heating operations across multiple indoor units.
Implementation Method 1
a plurality of intermediate heat exchangers for performing heat exchange between refrigerant and a heat medium
Implementation Method 2
an opening degree of each of the expansion devices is controlled in such a manner that a differential pressure between a refrigerant pressure detected by the high-pressure detecting device and a refrigerant pressure detected by the intermediate-pressure detecting device is greater than or equal to a set value
Implementation Method 3
a heat source unit including a compressor and an outdoor heat exchanger
Data Source
AI summary
An object is to provide a refrigeration cycle apparatus that does not cause unevenness of capacity among branch units and a failure in controlling a refrigerant circuit. At least one of branch units is a first branch unit having a minimum pressure loss in distribution of refrigerant in a high-pressure refrigerant pipe between a heat source unit and the branch units, and at least another one of the branch units is a second branch unit having a maximum pressure loss in distribution of refrigerant in the high-pressure refrigerant pipe between the heat source unit and the branch units. An opening degree of an expansion device is controlled in such a manner that a differential pressure between a refrigerant pressure detected by a high-pressure detecting device of the first branch unit and a refrigerant pressure detected by an intermediate-pressure detecting device is greater than or equal to a set value ΔPHM.