Intermediate Heat Exchanger Flow Control to Prevent AC Freezing
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Solution Overview
Problem
In air-conditioning systems with a small thermal load or fewer indoor units, pressure loss in the heat medium circuit increases, leading to insufficient flow rate of the heat medium to the intermediate heat exchanger, which can cause freezing during cooling operations.
Innovation Solution
The air-conditioning apparatus includes a refrigerant circuit and a heat medium circuit with an intermediate unit that uses flow control devices and controllers to regulate the flow rate of the heat medium, ensuring it meets a minimum flow rate by adjusting the opening degree of the flow control devices in non-operational indoor units to reduce pressure loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of indoor units in operation is small, then the thermal load is reduced, but the pressure loss in the heat medium circuit increases and the flow rate to the intermediate heat exchanger becomes insufficient
Solution Approach 1:
The flow control device dynamically adjusts the opening degree based on the number of operating indoor units and thermal load conditions. The intermediate controller receives operation status signals from indoor units and automatically modulates the flow control device to maintain adequate heat medium flow rate to the intermediate heat exchanger, preventing freezing while adapting to varying system demands.
Solution Approach 2:
The system implements feedback control where the intermediate controller monitors the operation status of indoor units and adjusts the flow control device accordingly. The controller receives signals about which indoor units are operating and uses this information to determine the appropriate opening degree of the flow control device, ensuring the heat medium flow rate remains sufficient under varying load conditions.
2Reliability
If the opening degree of the flow control device is increased, then the flow rate of heat medium increases, but the pressure loss control becomes challenging
Solution Approach 1:
The system changes the opening degree parameter of the flow control device based on operating conditions. The intermediate controller calculates the appropriate opening degree as a percentage (0-100%) that balances flow rate requirements with pressure loss constraints, adjusting this parameter dynamically according to the number of operating indoor units and thermal load demands.
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 effectively increases the flow rate of the heat medium to the intermediate heat exchanger, preventing freezing and ensuring stable operation by reducing pressure loss and eliminating the need for costly bypass systems.
Implementation Method 1
an intermediate unit located in the refrigerant circuit and the heat medium circuit and configured to exchange heat between the refrigerant and the heat medium
Implementation Method 2
Each of the plurality of indoor units includes a flow control device configured to regulate a flow rate of the heat medium leaving a corresponding one of the plurality of indoor units
Implementation Method 3
a circulation device configured to circulate the heat medium between the intermediate heat exchanger and each of the plurality of indoor units
Data Source
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AI summary
An air-conditioning apparatus includes an outdoor unit, multiple indoor units, and an intermediate unit. The indoor units each include a flow control device and an indoor controller. The intermediate unit includes an intermediate heat exchanger, a circulation device, and an intermediate controller. When at least one indoor unit starts operating, the intermediate controller determines whether a flow rate of a heat medium flowing into the intermediate heat exchanger is greater than or equal to a minimum flow rate. In response to determining that the flow rate is less than the minimum flow rate, the intermediate controller transmits an open instruction signal, representing an instruction to increase the opening degree of the flow control device, to the indoor controller of the indoor unit that is in a non-operation state. The indoor controller increases the opening degree of the flow control device in response to the received open instruction signal.