Refrigeration Cycle Bypass Flow Control for Efficient Defrosting
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Solution Overview
Problem
Conventional refrigeration cycle apparatuses do not effectively utilize the bypass circuit during defrosting operations, leading to inefficient defrosting times and energy usage when the evaporator is frosted.
Innovation Solution
The refrigeration cycle apparatus includes a bypass passage and a control device that reduces the refrigerant flow rate through the bypass passage before defrosting, increasing the enthalpy and discharge temperature of the compressor, thereby enhancing heat accumulation and reducing pressure loss, allowing for efficient defrosting while maintaining operational efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bypass circuit is utilized during normal heating/cooling operation, then heating/cooling ability and coefficient of performance are enhanced, but the bypass circuit cannot be effectively utilized during defrosting operation
Solution Approach 1:
The bypass expansion valve is dynamically controlled to adjust the bypass flow rate according to operational requirements. During normal operation, the valve maintains a flow rate that optimizes heating/cooling performance. During defrosting operation, the control device adjusts the valve to reduce the bypass flow rate to a predetermined value or close to zero, enabling effective utilization of the bypass circuit for defrosting purposes.
Solution Approach 2:
The system changes the operational parameters of the bypass circuit based on the required function. By adjusting the bypass flow rate parameter through the bypass expansion valve, the system transitions between normal heating/cooling mode and defrosting mode, allowing the same bypass circuit to serve multiple functions effectively.
2Temperature
If the bypass flow rate is reduced before defrosting, then heat accumulation in compressor and high-pressure refrigerant circuit is increased, but the refrigerant flow through the bypass passage is reduced
Solution Approach 1:
Before initiating the defrosting operation, the control device preliminarily reduces the bypass flow rate through the bypass expansion valve. This preliminary action allows heat to accumulate in the compressor body and high-pressure refrigerant circuit, preparing the system for efficient defrosting by ensuring sufficient thermal energy is available when the defrosting operation commences.
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 enables a shorter defrosting time and improved energy savings by effectively utilizing the bypass circuit during frost events, increasing heat accumulation in the compressor and high-pressure refrigerant circuit, and optimizing heat transfer during defrosting operations.
Implementation Method 1
a bypass expansion apparatus connected to the bypass passage located on an upstream side from the supercooling heat exchanger; and a control device, wherein the control device executes a heating operation for heating a utilization heat medium in the radiator, and a defrosting operation for removing frost formed on the evaporator by heat of refrigerant, and the control device executes a heat accumulating operation by controlling the bypass expansion apparatus for reducing a flow rate of refrigerant flowing through the bypass passage
Implementation Method 2
a compressor 111 in the refrigeration cycle apparatus 100. When a normal heating/cooling operation is carried out, target temperature Td (target) of a discharge pipe of the compressor is set from an evaporator inlet temperature Te detected by the temperature sensor 142
Implementation Method 3
a radiator 112, a supercooling heat exchanger 113, a main expansion valve 114 and an evaporator 115. The refrigeration cycle apparatus 100 includes a temperature sensor 141 for detecting temperature (compressor discharge pipe temperature) Td of refrigerant discharged from the compressor 111
Implementation Method 4
a supercooling heat exchanger is provided in a refrigerant circuit on the downstream side from the radiator, a portion of main stream refrigerant is expanded and is made to flow into the supercooling heat exchanger, and the main stream refrigerant which flows out from the radiator is supercooled
Implementation Method 5
an evaporator 115. The refrigerant circuit 110 is configured by annularly connecting, to one another through a pipe, a compressor 111, a radiator 112, a supercooling heat exchanger 113, a main expansion valve 114 and an evaporator 115
Implementation Method 6
a bypass expansion apparatus connected to the bypass passage located on an upstream side from the supercooling heat exchanger
Data Source
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AI summary
A refrigeration cycle apparatus includes: a refrigerant circuit 2 configured by annularly connecting, to one another through a refrigerant pipe, a compressor 21, a radiator 22, a supercooling heat exchanger 23, a main expansion valve 24 and an evaporator 25 in this order; a bypass passage 3 which is connected to the compressor 21 or to the refrigerant circuit 2; and a control device 4. Before a defrosting operation for removing frost formed on the evaporator 25 by heat of refrigerant is started, the control device 4 executes a heat accumulating operation for reducing a flow rate of refrigerant flowing through the bypass passage 3, thereby increasing a heat accumulation amount. Therefore, also when frost is formed on the evaporator 25, it is possible to effectively utilize the bypass passage 3, the defrosting operation is efficiently carried out, and it is possible to enhance energy saving performance and comfort.