Test chamber and method for conditioning of air
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Solution Overview
Problem
Existing test chambers face challenges in maintaining stable operating behavior due to varying cooling capacity requirements across a wide temperature range from -70 °C to +180 °C, leading to insufficient supercooling and potential critical operating states.
Innovation Solution
Incorporating a control device with a pressure sensor and temperature sensor in the cooling circuit to regulate the second expansion element, ensuring sufficient subcooling by adjusting refrigerant flow based on measured pressure and temperature, thereby preventing excessive suction gas temperature drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a zeotropic refrigerant mixture with carbon dioxide is used to achieve temperatures down to -70°C, then the temperature range is extended, but a comparatively large temperature glide results which is undesirable
Solution Approach 1:
The patent implements a control device that continuously monitors the temperature at the heat exchanger and adjusts the expansion element accordingly. This feedback mechanism compensates for the temperature glide of zeotropic refrigerant mixtures, maintaining stable evaporation temperatures and preventing excessive temperature variations that would otherwise occur with carbon dioxide-based refrigerants operating in the -70°C range.
2Temperature
If a bypass with a second expansion element is used to increase subcooling by lowering suction gas temperature, then greater subcooling is achieved, but the operating behavior becomes unstable across wide temperature ranges
Solution Approach 1:
The control device uses feedback from temperature sensors to dynamically regulate the second expansion element, ensuring that subcooling is optimized without causing instability. The system adjusts the bypass refrigerant flow based on real-time temperature measurements, preventing the operating behavior from becoming unstable across the wide temperature range from -70°C to +180°C.
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 ensures stable operating behavior and sufficient subcooling, preventing critical states in the cooling device by dynamically controlling the second expansion element, thus maintaining reliable refrigerant flow and temperature control across the temperature range.
Implementation Method 1
The internal heat exchanger cools or so-called sub-cools the liquefied refrigerant on the high-pressure side
Implementation Method 2
a first expansion element and an internal heat exchanger
Implementation Method 3
heat exchangers are arranged for heating or cooling the air flowing through the circulating air duct or the test space
Data Source
Figure 1
Figure 2
AI summary
The invention relates to a method and a test chamber for conditioning air, comprising a temperature-insulated test chamber (13) that can be closed off from the environment for receiving test material, and a temperature control device for temperature control of the test chamber, wherein, by means of the temperature control device, a temperature in a temperature range of -40 °C to +180 °C is maintained within the test chamber by means of a cooling device (10) with a cooling circuit (11) with a zeotropic refrigerant, a heat exchanger (14) arranged in the test chamber, a compressor (15), a condenser (16), a first expansion element (17) and an internal heat exchanger (18), wherein the internal heat exchanger is located on a high-pressure side (19) of the cooling circuit in a flow direction upstream of the first expansion element and downstream of the condenser, and on a low-pressure side (20) of the cooling circuit in the flow direction downstream of the heat exchanger and upstream of the compressor.is connected, wherein the cooling circuit has a bypass (26) with at least one second expansion element (28), wherein the bypass is connected on the high-pressure side downstream of the condenser and upstream of the internal heat exchanger in the flow direction, and on the low-pressure side downstream of the heat exchanger and upstream of the internal heat exchanger, wherein a control device of the temperature control device with a pressure sensor (30) on the high-pressure side and with a temperature sensor (31) on the high-pressure side downstream of the internal heat exchanger in the cooling circuit controls the second expansion element as a function of a pressure measured at the pressure sensor and a temperature measured at the temperature sensor.