Improved cooling system control
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Solution Overview
Problem
Conventional compressor cooling systems experience efficiency losses due to varying refrigerant mass flow rates through capillary tubes, which are not optimized for the compressor's on- and off-phases, leading to energy inefficiencies and increased start torque requirements.
Innovation Solution
A valve is strategically controlled in the refrigerant flow path between the condenser and evaporator, opening a variable time before the compressor on-phase and closing a variable time before the off-phase, based on external parameters such as ambient temperature, to optimize refrigerant flow and reduce energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a valve is closed during compressor off-phase to prevent refrigerant migration, then energy loss from refrigerant migration is reduced, but the compressor must start against a larger pressure difference between condenser and evaporator
Solution Approach 1:
The valve is opened a predetermined time before the compressor is scheduled to start, allowing pressure equalization between condenser and evaporator to occur in advance. This preliminary action reduces the pressure difference the compressor must overcome at startup, while the valve remains closed during the actual off-phase to prevent refrigerant migration.
2Force
If the valve is opened early before compressor on-phase to equalize pressure, then start torque requirement is reduced, but refrigerant flow rate at the start of compressor on-phase becomes suboptimal
Solution Approach 1:
The valve opens a predetermined time before compressor start to equalize pressure and reduce start torque. The predetermined time is calculated to balance two competing needs: allowing sufficient pressure equalization while ensuring the valve closes before the compressor actually starts, thereby optimizing the refrigerant mass flow rate at the beginning of the on-phase.
3Device complexity
If the valve timing is fixed, then control system is simple, but energy efficiency cannot be optimized for varying operating conditions
Solution Approach 1:
The controller determines the predetermined opening time before compressor start based on feedback from sensors monitoring system conditions such as pressure differential, temperature, and compressor runtime. This feedback mechanism allows the valve timing to be dynamically optimized for varying operating conditions while maintaining reasonable control system complexity.
Solution Approach 2:
The valve timing transitions from a fixed predetermined time to a dynamic value that varies with operating conditions. The controller adjusts the opening time before compressor start based on real-time system state, enabling energy efficiency optimization without requiring overly complex control architecture.
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 enhances energy efficiency by aligning refrigerant flow with optimal operating conditions, reducing energy consumption and improving compressor start conditions, particularly in systems with multiple evaporators.
Implementation Method 1
the refrigerant mass flow rate through the capillary tube is a function of evaporator and condenser pressure. When the pressure difference between evaporator and condenser is high the flow rate is high, and vice versa.
Implementation Method 2
use a capillary tube to reduce the pressure of the refrigerant flowing from condenser to evaporator
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
Described is, among other things, a cooling system comprising a compressor, a condenser and an evaporator wherein a refrigerant is circulated is provided. The cooling system further comprises a valve interconnected in the flow of the refrigerant from the condenser to the evaporator. The valve is operatively controlled to a first, open, state when the compressor is in an on-phase and to a second, closed, state when the compressor is in an off state by a controller. The controller is adapted to control the valve to operate in accordance with at least one of: - opening (401) the valve a first variable time period before the compressor is switched to an on-phase; where the first variable time period is set in response to an external parameter obtained by the controller, and/or - closing (409) the valve a second variable time period before the compressor is switched to an off-phase, where the second variable time period is set in response to an external parameter obtained by the controller.