Refrigeration system comprising a test chamber with temperature and humidity control
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Solution Overview
Problem
Current temperature and humidity control systems in test chambers face challenges in maintaining high temperature/humidity conditions, especially when a live load generates heat, as they either limit temperature/humidity ranges or compromise overall utility by increasing cooling loads and requiring continuous monitoring and correction.
Innovation Solution
A refrigeration system using a closed-loop vapor refrigerant circuit with a temperature-controlled coil that mixes superheated vapor and liquid refrigerant, allowing for efficient cooling without moisture loss and accommodating higher heat dissipation by regulating refrigerant flow through control valves, thereby reducing the need for additional steam and improving system efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separate cooling coil is used within the chamber workspace to maintain temperature above freezing point, then the cooling coil temperature is maintained above freezing point, but the cooling load increases significantly due to condensation and latent heat of condensation
Solution Approach 1:
The patent changes the temperature parameter of the refrigerant by mixing cold refrigerant from the evaporator with hot refrigerant from the compressor discharge line. This creates a refrigerant mixture at an intermediate temperature that can cool the chamber without causing excessive condensation, thereby reducing the cooling load while maintaining coil temperature above freezing.
Solution Approach 2:
The patent introduces a hot gas bypass line as an intermediary element that allows hot refrigerant vapor to mix with cold refrigerant. This intermediary hot gas serves as a temperature buffer, preventing the cooling coil from becoming too cold and causing condensation, thus reducing the overall cooling energy requirement.
2Loss of substance
If steam is added to replace condensed moisture to maintain humidity, then humidity is maintained, but the sensible heat from steam increases the cooling load
Solution Approach 1:
By changing the refrigerant temperature parameter through hot gas mixing, the system reduces condensation on the cooling coil. This minimizes moisture loss from the chamber air, thereby reducing the amount of steam needed for humidity replacement and the associated cooling load from steam condensation.
3Temperature
If the evaporating pressure is set based on the lowest temperature required, then the temperature range is covered, but the cooling coil temperature is significantly below dew point at high temperature/humidity conditions, resulting in condensation
Solution Approach 1:
The patent dynamically changes the refrigerant temperature parameter by adjusting the mix ratio of cold and hot refrigerant. This allows the system to maintain the lowest temperature capability when needed while raising the cooling coil temperature above the dew point during high temperature/humidity conditions, preventing condensation.
Solution Approach 2:
The system transitions from a static evaporating pressure setting to a dynamic refrigerant temperature control system. The hot gas bypass valve dynamically adjusts the refrigerant temperature based on chamber conditions, enabling the cooling coil temperature to adapt and stay above the dew point when necessary, preventing condensation while maintaining temperature range coverage.
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 system efficiently maintains temperature and humidity set-points with reduced moisture loss and increased heat dissipation capacity, enhancing the utility of test chambers without compromising other operational modes.
Implementation Method 1
a temperature-controlled coil in a load space of an environmental test chamber
Implementation Method 2
The refrigerant is expanded from a liquid to a vapor at a controlled pressure. The evaporating pressure is set based on the lowest temperature required
Implementation Method 3
The refrigerant is expanded from a liquid to a vapor at a controlled pressure. The evaporating pressure is set based on the lowest temperature required for the temperature/humidity mode of operation
Implementation Method 4
a vapor refrigerant circulating through a closed loop system is preconditioned by mixing the vapor refrigerant with a liquid refrigerant
Implementation Method 5
When cooling is required at the highest temperature/humidity combination in the operational range, a portion of the cooling coil temperature is significantly below the dew point of the air stream within the chamber, resulting in condensation
Data Source
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AI summary
A test chamber that is capable of operating in a mode where the temperature of the chamber is efficiently cooled without removing a substantial amount of moisture from the air. The test chamber includes a structure defining a work space having air, and a temperature control system. The temperature control system includes a heat exchanger positioned to communicate with the air in the work space, a source of cold fluid coupled to the heat exchanger, a source of hot fluid coupled to the heat exchanger, and a controller for controlling a mixture of cold fluid and hot fluid entering the heat exchanger The controller is programmed such that the temperature of the mixture entering the heat exchanger is controlled to limit a temperature differential between the heat exchanger and the air in the work space