Refrigeration device
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Solution Overview
Problem
In refrigeration devices, the compressor operation frequency is difficult to reduce during low internal load periods in cooling mode, which hinders the increase of the coefficient of performance (COP) due to the lower target evaporation temperature settings.
Innovation Solution
A refrigeration device with a compressor control system that adjusts the target evaporation temperature based on the internal load conditions, increasing it when the low internal load period is detected to reduce compressor operation frequency and enhance COP, while preventing excessive temperature increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target evaporation temperature is set lower to account for pressure loss in pipes, then the suction temperature can be maintained at the target value, but the compressor operation frequency cannot be reduced during low internal load periods
Solution Approach 1:
The patent applies dynamics by making the target evaporation temperature adjustable rather than fixed. The control device dynamically changes the target evaporation temperature based on operational phase (pull-down period vs. stable period) and compressor frequency index, allowing the system to adapt between maintaining reliable suction temperature control and enabling compressor frequency reduction for efficiency.
Solution Approach 2:
The patent changes the parameter of target evaporation temperature based on different operational conditions. During the pull-down period, a lower target temperature is used to ensure adequate cooling capacity, while during stable periods with low load, the target temperature is raised to enable compressor frequency reduction and improve COP, thus resolving the contradiction through parameter adaptation.
2Loss of energy
If the target evaporation temperature is increased to reduce compressor operation frequency, then energy efficiency improves, but the cooling capability may become insufficient
Solution Approach 1:
The patent applies preliminary action by ensuring adequate cooling capacity during the pull-down period through lower target evaporation temperature settings before transitioning to energy-efficient operation. This preliminary cooling phase prepares the system so that subsequent higher target temperatures during stable periods do not compromise overall cooling effectiveness.
Solution Approach 2:
The patent implements periodic action by alternating between different target evaporation temperature strategies based on operational phase. During pull-down periods, lower temperatures ensure cooling capability, while during stable periods with low compressor frequency index, higher temperatures improve COP, creating a periodic cycle that balances both requirements over time.
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 effectively reduces compressor operation frequency during low internal load periods, increasing the refrigeration device's coefficient of performance and maintaining sufficient cooling capability, thus improving energy efficiency and operational stability.
Implementation Method 1
a heat-source-side unit (11) including a compressor (21a)
Implementation Method 2
a heat-source-side heat exchanger (23) functioning as a condenser
Implementation Method 3
a utilization-side heat exchanger (51) to cool the internal space
Implementation Method 4
a refrigerant circuit (15) through which a refrigerant circulates
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The compressor control section (83) controls an operation frequency (FQ) of a compressor (21a) so that in a cooling mode, a temperature of a refrigerant sucked into the compressor (21a) is equal to a target evaporation temperature (Te). A target temperature setting section (84) sets the target evaporation temperature (Te) to be equal to a reference temperature (Teref) lower than a set internal temperature (Tset) during a pull-down period (PD) for reducing the internal temperature (Tr), which has elapsed since the start of the cooling mode. The target temperature setting section (84) corrects the target evaporation temperature (Te) so that if, after the pull-down period (PD) has elapsed, a frequency index value (FQi) dependent on the operation frequency (FQ) of the compressor (21a) during a period of time during which the utilization-side unit (12) is placed in the cooling state is above a predetermined reference value (FQref), the target evaporation temperature (Te) is higher than the reference temperature (Teref).