Refrigeration appliance and method in which the rotational speed of the compressor is controlled based on the temperature of a first temperature zone independently of a temperature of other temperature zones
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Solution Overview
Problem
Refrigeration appliances with multiple temperature zones face challenges in maintaining stable temperature control due to unsatisfied cooling requirements leading to undesirable temperature fluctuations, as existing systems redistribute cooling performance across zones, failing to account for changing environmental conditions.
Innovation Solution
A refrigeration system with a compressor and evaporators connected in series, featuring a controllable throttle point upstream of the first evaporator and a compressor regulator that adjusts compressor speed based on the first temperature zone's conditions, while a separate throttle regulator independently controls the second throttle point to manage cooling in the second zone, using proportional-integral (PI) control to adjust for temperature deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the throttling is increased at the expansion valve upstream of an evaporator to satisfy cooling requirements in one temperature zone, then the evaporation temperature in that evaporator falls, but the mass flow of refrigerant remains unchanged, causing cooling performance to be withheld from other temperature zones and leading to temperature fluctuations
Solution Approach 1:
The invention divides the control of refrigerant flow into two independent parts: a controllable expansion valve upstream of each evaporator for local temperature control, and a second controllable expansion valve downstream of each evaporator for maintaining overall mass flow balance. This segmentation allows independent optimization of local cooling performance while preserving global system stability.
Solution Approach 2:
The invention applies different control strategies to different parts of the refrigerant circuit. The first expansion valve is controlled locally based on the cooling requirements of its associated evaporator, while the second expansion valve is controlled to maintain the overall mass flow. This local quality approach allows each part to be optimized for its specific function.
2Productivity
If the rotational speed of the compressor is increased to increase the evaporation rate in the first evaporator, then the cooling performance in the first temperature zone improves, but the quantity of liquid refrigerant in the second evaporator changes over time, potentially affecting its temperature
Solution Approach 1:
The invention implements feedback control by monitoring the temperature of each temperature zone and adjusting the degree of opening of the first controllable throttle point accordingly. The controller increases the degree of opening when the temperature rises above the set point and decreases it when the temperature falls below the set point, maintaining stable refrigerant distribution while allowing compressor speed adjustments for productivity.
3Adaptability or versatility
If a single control system manages cooling performance redistribution across multiple temperature zones, then cooling requirements in one zone can be satisfied, but temperature fluctuations occur in other zones due to unavoidable redistribution
Solution Approach 1:
The invention segments the control system into multiple independent controllers, each managing a specific evaporator-throttle point pair. Each controller independently adjusts the degree of opening of its associated first controllable throttle point based on local temperature feedback, eliminating the need for cooling performance redistribution and preventing temperature fluctuations in other zones.
Solution Approach 2:
The controller is designed with multi-functionality to independently manage multiple temperature zones simultaneously. Each controller can adjust the degree of opening of its associated throttle point while being influenced by the operational state of other throttle points, allowing universal application across all temperature zones without interference.
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 allows for simple and stable temperature control across multiple zones by independently managing the compressor speed and throttle points, ensuring precise temperature regulation in each zone without affecting other zones, thereby minimizing temperature fluctuations.
Implementation Method 1
a compressor (10)
Implementation Method 2
a first evaporator (6) for cooling a first temperature zone (1), a second evaporator (7) for cooling a second temperature zone (2)
Implementation Method 3
a first controllable throttle point (20) in the refrigerant circuit is connected upstream of the first evaporator (6) and downstream of the second evaporator (7)
Data Source
AI summary
A refrigeration appliance has at least a first and a second temperature zone and a refrigerant circuit that includes a compressor, a first evaporator for cooling the first temperature zone and a second evaporator for cooling the second temperature zone. The first evaporator is serially connected downstream of the second evaporator in the refrigerant circuit, and a controllable throttle point is arranged upstream of the first evaporator and downstream of the second evaporator in the refrigerant circuit. A compressor controller is configured to control the rotational speed of the compressor on the basis of the temperature in the first temperature zone.