Cool Gas Drying Circuit With Superheat Control for Compressor Protection
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Solution Overview
Problem
Existing cool drying methods for gases, particularly compressed air, face issues with corrosion and premature wear due to condensation, requiring expensive and complex liquid separators to prevent liquid coolant ingestion by the compressor, which can still fail during transitional situations.
Innovation Solution
A method and device utilizing a closed cooling circuit without a liquid separator, employing an electronic expansion valve and an electronic hot gas bypass valve to ensure the coolant is always superheated at the compressor input, eliminating the need for a liquid separator by controlling the expansion valve to maintain superheating and using a hot gas bypass to manage evaporator pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a liquid separator is integrated in the cooling circuit to prevent liquid coolant from reaching the compressor, then the reliability of the compressor is improved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical liquid separator with an electronic control system that uses an electronic expansion valve and hot gas bypass valve to prevent liquid coolant from reaching the compressor. The electronic expansion valve precisely controls coolant expansion to ensure complete evaporation, while the hot gas bypass valve provides additional protection during transitional situations, eliminating the need for mechanical separation devices.
Solution Approach 2:
The patent changes the control parameter from passive mechanical separation to active electronic control of coolant superheating. By precisely controlling the expansion valve to maintain a specific degree of superheating (typically 5-15°C), the system ensures that coolant is completely evaporated before reaching the compressor, preventing liquid ingestion without requiring a liquid separator.
2Temperature
If a thermostatic expansion valve is used to expand coolant, then the cooling effect is improved, but liquid coolant may still reach the compressor during transitional situations
Solution Approach 1:
The patent implements feedback control by using temperature and pressure sensors to monitor the state of coolant after the evaporator. The electronic expansion valve receives feedback signals based on the measured degree of superheating and automatically adjusts its opening to maintain the desired superheating level, ensuring reliable prevention of liquid coolant reaching the compressor during all operating conditions.
Solution Approach 2:
The patent applies preliminary action by ensuring that the coolant is pre-heated and completely evaporated in the evaporator before being delivered to the compressor. The electronic expansion valve is controlled to maintain sufficient superheating (5-15°C) as a safety margin before compressor intake, preventing liquid coolant ingestion in advance rather than relying on post-compression protection.
3Reliability
If the expansion valve is controlled to maintain superheating, then liquid coolant is prevented from reaching the compressor, but the control complexity increases
Solution Approach 1:
The patent replaces complex mechanical control mechanisms with electronic control systems. The electronic expansion valve uses electronic actuators and control circuits to precisely regulate coolant flow based on sensor feedback, providing more accurate and reliable superheating control than mechanical thermostatic expansion valves while enabling better protection against liquid coolant ingestion.
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 prevents liquid coolant from reaching the compressor, simplifying and cost-reducing the device while ensuring reliable operation by maintaining coolant superheating during startup and shutdown, thus preventing compressor damage and reducing equipment complexity.
Implementation Method 1
controlling this electronic expansion valve such that the coolant is always superheated at the input of the compressor
Implementation Method 2
expansion means with a bypass pipe with a hot gas bypass valve therein that connects the outlet of the compressor to an injection point upstream from the compressor
Implementation Method 3
water vapour in the gas is condensed by guiding the gas through the secondary section of a heat exchanger whose primary section forms the evaporator
Implementation Method 4
heat exchanger whose primary section forms the evaporator of a closed cooling circuit
Implementation Method 5
a compressor that is installed in the cooling circuit downstream from the evaporator
Implementation Method 6
followed by a condenser and expansion means through which the coolant can circulate
Data Source
Figure 1~2
AI summary
Method for cool drying gas by guiding gas through the secondary section (9) of a heat exchanger (2) whose primary section forms the evaporator (3) of a closed cooling circuit (4) in which a coolant can circulate by means of a compressor (5) that is followed by a condenser (6) and expansion means (7) through which the coolant can circulate, whereby use is made of an air-cooled condenser (6) with a frequency controlled fan (19), and the method comprises the step of controlling the speed of the aforementioned fan (19) so that the condenser pressure (pc) is kept equal to a target value.