Outdoor Unit Pump-Down Control for Faster Refrigerant Recovery
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Solution Overview
Problem
The existing refrigeration apparatuses face challenges in reducing refrigerant recovery time during a pump down operation, as the refrigerant recovery progresses and the condensation temperature approaches the outside air temperature, leading to inefficiencies in the condensation process.
Innovation Solution
The outdoor unit of the refrigeration cycle apparatus includes a first flow path with a compressor and condenser, a second flow path branching from the condenser to return refrigerant to the compressor, a second expansion device, a receiver, and a flow rate control valve. The control state of the compressor and flow rate control valve is set to close the valve initially and then open it to optimize the heat exchanger efficiency during refrigerant recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If refrigerant recovery progresses in the pump down operation, then more refrigerant is recovered to the outdoor unit, but the condensation temperature becomes close to the outside air temperature and the refrigerant becomes less liquefied in the condenser, leading to increased recovery time
Solution Approach 1:
The patent introduces a heat exchanger as an intermediary device to transfer heat from the refrigerant in the second flow path to the refrigerant in the first flow path. This mediator enables efficient heat exchange between the two refrigerant streams, maintaining condensation efficiency even when the condensation temperature approaches the outside air temperature, thereby reducing the overall pump down operation time while recovering more refrigerant.
Solution Approach 2:
The patent divides the refrigerant flow into two separate flow paths: the first flow path for main refrigerant circulation through the condenser, and the second flow path for extracting and reheating refrigerant before returning it to the compressor. This segmentation allows independent control and optimization of each path, enabling the system to maintain efficient condensation while managing the pump down process effectively.
2Temperature
If the condensation temperature approaches the outside air temperature during refrigerant recovery, then the temperature difference for heat exchange decreases, but the refrigerant liquefaction efficiency deteriorates
Solution Approach 1:
The heat exchanger acts as an intermediary that transfers heat from the refrigerant in the second flow path (which has been extracted and is being reheated) to the refrigerant in the first flow path (which is undergoing condensation). This intermediary heat exchange mechanism compensates for the reduced temperature difference, maintaining refrigerant liquefaction efficiency even when the condensation temperature approaches the outside air temperature.
Solution Approach 2:
The patent changes the temperature parameter of the refrigerant by extracting it from the first flow path, reheating it in the heat exchanger using heat from another refrigerant stream, and returning it to the compressor. This parameter change (temperature increase) of the extracted refrigerant allows it to serve as a heat source, maintaining the overall heat exchange efficiency and refrigerant liquefaction rate during the pump down operation.
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 maintains heat exchanger efficiency and reduces the time required for refrigerant recovery by promoting efficient condensation even when the condensation temperature approaches the outside air temperature.
Implementation Method 1
a heat exchanger having a first passage and a second passage and configured to exchange heat between the refrigerant flowing in the first passage and the refrigerant flowing in the second passage
Implementation Method 2
a condenser disposed on the first flow path
Data Source
Figure 1
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AI summary
An outdoor unit (2) includes: a first flow path (F1); a second flow path (F2); a second expansion device (71), a receiver (73), and a flow rate control valve (72) disposed on the second flow path (F2) in order from a branch point; a heat exchanger (30); and a controller (100). The heat exchanger (30) exchanges heat between refrigerant flowing in a first passage (H1) and the refrigerant flowing in a second passage (H2). When a pump down operation for recovering the refrigerant to the receiver (73) is started, the controller (100) is configured to control a control state of a compressor (10) and the flow rate control valve (72), at a first time point, to a first state in which the flow rate control valve (72) is closed while the compressor (10) is operated. During the pump down operation, the controller (100) is configured to transition, at a second time point after the first time point, the control state from the first state to a second state in which the flow rate control valve (72) is opened while the compressor (10) is operated.