Estimation apparatus of heat transfer medium flow rate, heat source machine, and estimation method of heat transfer medium flow rate
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Solution Overview
Problem
Existing methods for estimating 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 and method that uses an aerodynamic characteristic map to compute the flow rate of a heat transfer medium by deriving parameters from suction volume and pressure measurements, eliminating the need for a flow meter by calculating the flow rate based on heat exchange between the refrigerant and the heat transfer medium in the evaporator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a flow meter is used to measure the flow rate of chilled water, then the flow rate can be accurately measured, but the cost increases significantly
Solution Approach 1:
The patent uses an intermediary substance (refrigerant) and its thermodynamic properties as a mediator to indirectly measure the chilled water flow rate. By measuring the refrigerant's state changes (temperature, pressure, enthalpy) in the evaporator and using heat balance equations, the system derives the chilled water flow rate without direct measurement, thus avoiding the need for expensive flow meters while maintaining measurement accuracy.
2Measurement precision
If multiple differential pressure sensors and flow sensors are provided to measure flow rates in each air conditioning machine, then the flow rate can be measured, but the device complexity and cost increase
Solution Approach 1:
The patent makes the refrigerant state measurements serve multiple functions: they are used not only for controlling the refrigeration system but also for calculating the chilled water flow rate. The same temperature and pressure sensors used for system control are repurposed for flow rate calculation through thermodynamic equations, eliminating the need for separate dedicated flow measurement devices.
Solution Approach 2:
The system uses its own operational parameters (refrigerant temperature, pressure, and enthalpy changes) to self-determine the chilled water flow rate. The refrigeration system's own thermodynamic behavior during operation provides the necessary information for flow rate calculation, without requiring external measurement devices.
3Measurement precision
If differential pressure sensors are used to measure differential pressure of the fluid, then the flow rate can be derived, but the cost and device complexity increase
Solution Approach 1:
The patent replaces mechanical/differential pressure-based flow measurement systems with a thermodynamic calculation approach. Instead of using pressure differential across an orifice or venturi, the system uses thermodynamic state changes of the refrigerant (enthalpy, temperature, pressure) and heat balance equations to calculate flow rate, substituting mechanical measurement with thermodynamic computation.
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 heat transfer medium flow rate without using a flow meter, reducing costs and component count, while maintaining operational efficiency.
Implementation Method 1
a compressor for compressing a refrigerant
Implementation Method 2
a condenser for condensing the compressed refrigerant using a heat source medium
Implementation Method 3
an evaporator for evaporating the condensed refrigerant and carrying out heat exchange between the refrigerant and a heat transfer medium
Implementation Method 4
carrying out heat exchange between the refrigerant and a heat transfer medium
Data Source
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 Ω reflecting a head of the compressor (12); a estimation portion of chilled water flow rate (30b) computes the variable Ω, derives the variable θ according to the variable Ω 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.