Outdoor Unit Ventilation Control for Flammable Refrigerant Leakage
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Solution Overview
Problem
Existing air-conditioning apparatuses for office buildings do not adequately address refrigerant leakage into outdoor unit housings, particularly with flammable refrigerants, leading to safety concerns and energy inefficiencies.
Innovation Solution
Incorporating an outdoor unit with a compressor, heat source side heat exchanger, and an outdoor unit air-sending device that maintains refrigerant concentration below a predetermined level by providing a ventilation air flow rate, preventing ignition and enhancing safety and energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If refrigerant circulation system is used between outdoor unit and relay unit, then refrigerant leakage into indoor side is prevented, but refrigerant leakage into outdoor unit housing is not addressed
Solution Approach 1:
The patent divides the outdoor unit housing into a sealed refrigerant circulation space and a ventilated air intake space. The housing includes a housing body with a refrigerant circulation space where the compressor and heat exchanger are located, and a separate air intake space that communicates with the exterior through an air intake port. This segmentation prevents refrigerant leakage into the indoor side while addressing refrigerant accumulation in the outdoor housing through dedicated ventilation pathways.
Solution Approach 2:
The patent introduces a air-sending device as an intermediary component that actively circulates air through the housing. The air-sending device includes a fan that draws external air through the air intake port and discharges it through an air discharge port, creating a continuous air flow that prevents refrigerant accumulation in the housing. This intermediary device mediates between the refrigerant circulation system and the external environment.
2Reliability
If solenoid valve blocks refrigerant passage upon leakage, then refrigerant leakage is stopped, but air flow rate through air-sending device is not specified
Solution Approach 1:
The patent incorporates a refrigerant concentration detection device that continuously monitors the refrigerant concentration in the housing and provides feedback to the control device. When the detected concentration exceeds a predetermined threshold, the control device activates the air-sending device to increase air flow and dilute the refrigerant concentration. This feedback mechanism ensures both reliable refrigerant leakage blocking and proper air flow rate control based on actual conditions.
Solution Approach 2:
The patent changes the operational parameters of the air-sending device based on detected refrigerant concentration levels. The control device adjusts the fan speed and air flow rate dynamically - operating at low speed under normal conditions and switching to high speed when refrigerant leakage is detected. This parameter adjustment optimizes both energy efficiency and safety.
3Object-affected harmful factors
If damper for discharging refrigerant is activated with air-sending device, then refrigerant concentration is reduced, but unit cannot operate while stopped
Solution Approach 1:
The patent designs the air-sending device and air intake/discharge ports to be continuously operational regardless of the refrigeration cycle operation state. The housing structure includes permanently installed air intake ports and air discharge ports that allow air flow even when the unit is stopped. The control device can activate the air-sending device independently of the compressor and refrigerant circulation, ensuring refrigerant concentration control is available at all times including during standby periods.
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 solution effectively maintains refrigerant concentration at safe levels, preventing ignition and ensuring high safety and energy efficiency even during refrigerant leakage, by using the outdoor unit air-sending device to control ventilation air flow rates based on the Lower Flammability Limit of the refrigerant.
Implementation Method 1
a heat source side heat exchanger exchanging heat between the refrigerant and air
Implementation Method 2
an outdoor unit air-sending device disposed at a position where the air is enabled to flow out of a housing to outside thereof, the outdoor unit air-sending device being driven to maintain the concentration of the refrigerant in the housing at or below a predetermined concentration
Data Source
AI summary
An outdoor unit includes a compressor that compresses a flammable refrigerant, a heat source side heat exchanger that exchanges heat between the refrigerant and air in an unconditioned space, an outdoor unit air-sending device disposed at a position where the air is enabled to flow out of a housing to the outside, the outdoor unit air-sending device being driven to maintain the concentration of the refrigerant in the housing at or below a predetermined concentration, and an outdoor unit controller that controls an operation of the compressor and an operation of the outdoor air-sending device. The outdoor unit controller allows the outdoor unit air-sending device to operate in order to maintain the concentration of the refrigerant at or below the predetermined concentration even when the compressor is stopped.