Chilled Water Flow Estimation Using Compressor Characteristic Maps
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Solution Overview
Problem
Existing methods for measuring the flow rate of heat transfer media in heat source machines, such as chillers, require expensive flow meters and multiple differential pressure sensors, making them costly and inefficient.
Innovation Solution
An estimation apparatus that computes the flow rate of the heat transfer medium using the suction volume of the compressor and aerodynamic characteristic maps, derived from preliminary tests, to determine the amount of heat exchanged between the refrigerant and the heat transfer medium, thereby eliminating the need for a flow meter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow meter is used to measure the flow rate of heat transfer medium, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical flow meter with a computational estimation system that uses compressor parameters (suction volume, head) and aerodynamic characteristic maps to calculate heat transfer medium flow rate. This substitution eliminates the need for direct mechanical measurement while achieving accurate flow rate determination through thermodynamic relationships.
Solution Approach 2:
The patent introduces aerodynamic characteristic maps as an intermediary between compressor parameters and heat transfer medium flow rate. These maps serve as a bridge that translates compressor operating conditions into flow rate estimates without requiring direct measurement of the heat transfer medium itself.
2Measurement precision
If multiple differential pressure sensors are used to measure flow rate, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the flow rate measurement function from the heat transfer medium circuit and relocates it to the refrigerant circuit. By measuring compressor parameters (which are already present in the system) and using aerodynamic characteristic maps, the system determines heat transfer medium flow rate without adding sensors to the heat transfer medium piping.
Solution Approach 2:
The patent makes the compressor parameters serve multiple functions: they are used both for compressor control and for estimating heat transfer medium flow rate. The aerodynamic characteristic maps enable these parameters to provide information about both refrigerant compression and heat transfer medium flow characteristics.
3Measurement precision
If flow meters and differential pressure sensors are installed, then flow rate measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, durable measurement instruments (flow meters and differential pressure sensors) with a low-cost computational approach using aerodynamic characteristic maps. The maps, once created through preliminary testing, can be used repeatedly without degradation, providing continuous accurate measurements at minimal cost.
Solution Approach 2:
The patent performs preliminary testing to create aerodynamic characteristic maps before actual operation. These maps contain pre-calculated relationships between compressor parameters and heat transfer medium flow rate, allowing the system to operate without expensive real-time measurement devices during normal operation.
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
Enables accurate computation of the heat transfer medium flow rate without using a flow meter, reducing costs and component count, while maintaining operational efficiency.
Implementation Method 1
a compressor (12) for compressing a refrigerant
Implementation Method 2
a condenser (14) for condensing a compressed refrigerant using a heat source medium
Implementation Method 3
an evaporator (24) for evaporating a condensed refrigerant and performing heat exchange with a heat transfer medium
Implementation Method 4
computing an amount of heat exchanged between the refrigerant and the heat transfer medium in the evaporator
Data Source
Figure 1
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AI summary
A flow rate of a heat transfer medium is computed without a flow meter. In a control apparatus (30), a storing portion (36) stores an aerodynamic characteristic map indicating a line causing a rotating stall and lines showing a sonic velocity in a refrigerant sucked in by a compressor (12) on a map displaying a variable θ reflecting a suction volume of the compressor (12) and a variable Q reflecting a head of the compressor (12); a estimation portion of chilled water flow rate (30b) computes the variable Q, derives the variable θ according to the variable Q from the map, computes a heat amount exchanged between the refrigerant and the chilled water in an evaporator (24) based on the suction volume of the compressor (12) according to the computed variable θ, and computes the flow rate of the chilled water based on the heat amount.