Electronic Expansion Valve Control for Stable Food Cooling Loads
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Solution Overview
Problem
Existing machines for producing and dispensing liquid or semiliquid food products, such as ice-creams and yogurts, face challenges in adapting quickly to varying thermal loads during whipping cycles, leading to overheating issues that affect operation stability and energy efficiency, and cannot effectively follow the dynamic temperature/pressure profiles required for food production.
Innovation Solution
A machine with a heat-adjustment system that includes a predictive control unit regulating an electronic expansion valve, using a PID control algorithm to manage overheating by continuously tracking load variations and adjusting the passage section of the valve based on real-time temperature and pressure measurements, ensuring stable overheating values and efficient use of the evaporator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thermostatic expansion valve is used to regulate refrigerant flow, then the valve stability improves, but the overall yield of the heat-adjustment system reduces due to overheating
Solution Approach 1:
The patent changes the control parameter from temperature-based (thermostatic valve) to pressure-based (electronic expansion valve with pressure sensor). This allows direct control of refrigerant flow based on evaporator pressure, eliminating the overheating delay and improving both valve stability and system yield simultaneously.
Solution Approach 2:
The patent replaces the mechanical thermostatic expansion valve with an electronic expansion valve controlled by an electronic control unit. This substitution enables precise electronic control of the valve opening based on real-time pressure feedback, resolving the contradiction between mechanical stability and system efficiency.
2Reliability
If the refrigerant overheating is increased to improve valve stability, then the valve operation becomes more stable, but the energy efficiency of the heat-adjustment system decreases
Solution Approach 1:
The patent implements a feedback control system where a pressure sensor continuously monitors evaporator pressure and sends signals to the electronic control unit. The controller adjusts the electronic expansion valve in real-time based on this feedback, maintaining optimal refrigerant flow without excessive overheating, thus preserving energy efficiency while ensuring stable operation.
3Temperature
If the electronic expansion valve passage section is reduced to lower refrigerant flow, then the overheating value decreases, but the system cannot adapt quickly enough to thermal load changes during whipping cycles
Solution Approach 1:
The patent employs a dynamic control system where the electronic expansion valve opening is continuously adjusted based on real-time pressure feedback during whipping cycles. This dynamic adjustment allows the system to quickly adapt to changing thermal loads while maintaining precise control over refrigerant flow and overheating values.
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 solution allows for quick adaptation to thermal load changes during whipping cycles, maintaining stable operation and energy efficiency, preventing cyclic oscillations and ensuring the quality of the produced foodstuff by dynamically adjusting the overheating set in response to temperature variations.
Implementation Method 1
The expansion valve has the function of lowering the temperature of the liquid coming out of the condenser bringing it from the condensation temperature to the evaporation temperature through pressure lowering
Implementation Method 2
an evaporator for cooling the foodstuff
Implementation Method 3
a compressor for compressing the refrigerant
Implementation Method 4
a condenser for condensing the refrigerant
Data Source
AI summary
A machine for producing and dispensing liquid or semiliquid foodstuffs, includes a heat-adjustment system including a thermal circuit within which a thermal fluid circulates. The thermal circuit includes a compressor, a condenser, an electronic expansion valve, an evaporator, and a control unit configured for determining a main parameter (SH) representative of instantaneous overheating of the thermal fluid coming out of the evaporator. A reference parameter (SHset) is determined as a function of a predetermined value (SHmin), and of an auxiliary value (DT) depending on a variation in time of the temperature (Tout) of the fluid coming out of the evaporator, and of the saturation temperature (Tsat) of the fluid coming out of the evaporator. An electric command signal (S) for the valve is generated as a function of a comparison between the main parameter (SH) and reference parameter (SHset).