Refrigerated Display Cabinet Pressure Control for Stable Air Temperature
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Solution Overview
Problem
Traditional horizontal refrigerated display cabinets experience temperature fluctuations due to On/Off cycles, leading to product drying and quality deterioration, and require frequent defrosting and humidity restoration, which are inefficient and costly.
Innovation Solution
A method that maintains continuous operation of the evaporator by regulating evaporation pressure based on real-time temperature measurements to stabilize air temperature within ±0.5°C, eliminating the need for On/Off cycles and defrosting, and maintaining humidity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If On/Off cycles are used to control evaporator operation, then energy consumption is reduced during off phases, but temperature fluctuations of 2-3°C occur causing product quality deterioration
Solution Approach 1:
The patent applies periodic defrosting cycles to the evaporator, where the evaporator is periodically switched off and heated to remove ice deposits. This periodic action prevents continuous ice buildup that would otherwise degrade air flow and heat exchange efficiency, while allowing the evaporator to operate continuously at reduced capacity rather than using aggressive On/Off cycling, thereby maintaining more stable temperatures.
Solution Approach 2:
The patent changes the operating parameters by maintaining the evaporator in continuous operation at partially loaded conditions rather than switching it off completely. By adjusting the refrigerant flow and using periodic defrosting, the system maintains evaporator temperatures above freezing point during operation, eliminating ice buildup and the associated temperature fluctuations in the display compartment.
2Power
If evaporator temperature is lowered to meet cooling demands, then cooling capacity increases, but ice forms on the evaporator requiring frequent defrosting
Solution Approach 1:
The patent changes the evaporator operating temperature parameter by maintaining it above the freezing point of water through continuous partial operation and periodic defrosting. This prevents ice formation on the evaporator surfaces while still achieving adequate cooling capacity through increased air circulation and heat exchange efficiency.
Solution Approach 2:
The patent implements periodic defrosting cycles where the evaporator is switched off and heated to remove ice deposits. This periodic maintenance allows the evaporator to operate at lower temperatures during cooling phases to meet high cooling demands, then restores efficiency by removing accumulated ice that would otherwise block air flow and reduce heat exchange.
3Reliability
If mechanical pressure valve is calibrated for maximum thermal loads, then product temperature protection is ensured, but air temperature fluctuations increase
Solution Approach 1:
The patent employs feedback control through temperature sensors that continuously monitor the air temperature in the display compartment and the evaporator temperature. This feedback allows the control system to adjust refrigerant flow and evaporator operation in real-time, maintaining product temperature protection while minimizing air temperature fluctuations by responding dynamically to actual thermal conditions rather than relying solely on fixed pressure valve calibration.
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 approach reduces temperature fluctuations, prevents ice formation, and maintains humidity, enhancing product quality and shelf life without the need for air humidifiers or electric resistors, improving energy efficiency and operational simplicity.
Implementation Method 1
a flow of air A is created through the evaporator which, cooled, is then forced towards the products on display inside the cabinet
Implementation Method 2
The air flowing through the evaporator thus deposits water on it in the form of crystals
Implementation Method 3
The air flowing through the evaporator thus deposits water on it in the form of crystals
Implementation Method 4
the evaporator is always active with continuous generation of cooling capacity... measuring over time the evaporation pressure of the refrigerant fluid at the evaporator
Data Source
Figure 1
Figure 2a~5
Figure 2b~7
AI summary
The invention relates to a method of controlling a horizontal refrigerated display cabinet (1), said cabinet (1) comprising at least one evaporator (2) belonging to a steam compression refrigerant circuit and ventilation means suitable to generate a flow of air which circulates between the evaporator (2) and the display compartment of said cabinet (1). The method is characterised by the fact that it keeps the evaporator (2) constantly active with generation of cooling capacity and that it comprises the following operating steps: a) fixing a set temperature for the air temperature leaving the evaporator (2); b)measuring over time the temperature of the air flow leaving the evaporator (2); c) measuring over time the evaporation pressure of the refrigerant fluid at the evaporator (2); wherein the control of the cabinet is conducted by continuously regulating the evaporation pressure of the refrigerant fluid at the evaporator (2) depending on the measured temperature values of the air so as to have the air flow leaving the evaporator (2) at a stable temperature at the set value in regular functioning conditions of the cabinet (1). The invention also relates to a refrigerated display cabinet (1) controllable by such method.