Refrigerated Space Temperature Control to Prevent Cargo Freezing
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Solution Overview
Problem
Current temperature control systems for refrigerated spaces, such as refrigerated trailers, fail to prevent cargo from freezing near discharge air vents while maintaining the set point temperature, often requiring complex fluid control systems and algorithms that interfere with each other.
Innovation Solution
A temperature control system that monitors discharge and return air temperatures, adjusts the target temperature to match the set point, and switches between heating and cooling modes to prevent freezing, using a heat exchange assembly and sensors to control the return air temperature, with a controller that adjusts the target temperature based on discharge air temperature drops below freezing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If discharge air temperature is reduced to maintain set point temperature, then cooling efficiency is improved, but cargo near discharge air vent freezes
Solution Approach 1:
The patent segments the temperature control into two independent control loops: one for return air temperature (maintaining set point) and one for discharge air temperature (preventing freeze). This segmentation allows each loop to optimize its function without interfering with the other, resolving the contradiction between maintaining set point temperature and preventing cargo freeze.
Solution Approach 2:
The patent introduces an intermediary control mechanism where the discharge air temperature is monitored and used to adjust the return air target temperature. This intermediary approach allows the system to respond to freeze conditions by modifying the return air set point, thereby preventing cargo freeze while maintaining overall temperature control.
2Reliability
If complex fluid control systems and combined algorithms are used to prevent cargo freezing, then freeze protection is improved, but control system complexity increases
Solution Approach 1:
The patent divides the control system into two separate, simple control loops rather than using a complex combined algorithm. The first loop controls return air temperature to maintain set point, and the second loop monitors discharge air temperature and adjusts return air target accordingly. This segmentation simplifies the control logic while maintaining effective freeze protection.
Solution Approach 2:
The patent implements a feedback mechanism where discharge air temperature is continuously monitored and feeds back to adjust the return air target temperature. This simple feedback loop provides reliable freeze protection without requiring complex algorithms, as the system automatically responds to temperature changes through the feedback connection between the two control loops.
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
Effectively prevents cargo from freezing by maintaining the refrigerated space temperature close to the set point, reducing the need for complex control systems and software, while ensuring the cargo remains at or near the desired temperature.
Implementation Method 1
a heat exchange assembly for heating the refrigerated space in a heat mode and cooling the refrigerated space in a cool mode
Implementation Method 2
a heat exchange assembly for heating the refrigerated space in a heat mode and cooling the refrigerated space in a cool mode
Implementation Method 3
a return air temperature sensor positioned in the return air flow path for sensing a return air temperature, a discharge air temperature sensor positioned in the discharge air flow path for sensing a discharge air temperature
Data Source
AI summary
A method for freeze protection for a temperature control system, and a temperature control system for controlling the temperature of a temperature-controlled space at a set point temperature. The method includes monitoring a discharge air temperature, monitoring a return air temperature, setting a target temperature to equal the set point temperature, controlling the return air temperature at the target temperature, and adjusting the target temperature based on the return air temperature when the discharge air temperature drops to one of at or below freezing.