Coolant Temperature Estimation Through Casing Lag Compensation
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Solution Overview
Problem
In coolers using liquid coolants, direct temperature measurement is costly due to waterproofing requirements, and indirect measurement through a casing leads to a time lag, making accurate coolant temperature control challenging.
Innovation Solution
A cooler system with a casing, temperature sensor attached to the casing, and an estimator that models the heat transfer as a first or second order lag system to estimate coolant temperature by calculating correction values based on differences in temperature measurements and flow rates, using a gain map to compensate for time lag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is submerged in the coolant to directly measure the coolant temperature, then the measurement precision is improved, but the device complexity increases due to waterproofing requirements and cost increases
Solution Approach 1:
The patent uses the casing as an intermediary medium to transfer temperature information from the coolant to the temperature sensor. The sensor measures the casing temperature rather than directly contacting the coolant, eliminating waterproofing requirements while maintaining measurement capability through thermal coupling between the casing and coolant
Solution Approach 2:
The patent creates a temperature copy by measuring the casing temperature which reflects the coolant temperature. Instead of directly measuring the coolant temperature, the system measures an equivalent temperature signal from the casing that is thermally coupled to the coolant, avoiding direct contact issues
2Device complexity
If a temperature sensor is attached to the casing to avoid direct coolant contact, then the device complexity is reduced, but a time lag occurs in temperature measurement
Solution Approach 1:
The patent implements a feedback mechanism where the estimated coolant temperature is continuously fed back to the control unit, which adjusts the cooler operation based on this feedback. The control unit uses the temperature difference between measured casing temperature and estimated coolant temperature to optimize cooling performance and compensate for the time lag
Solution Approach 2:
The patent performs preliminary temperature estimation by using the control unit to calculate the coolant temperature based on the casing temperature measurement and heat transfer modeling. This preliminary estimation allows the system to proactively adjust cooling operations before the actual coolant temperature reaches the target, compensating for the inherent time lag in thermal response
3Adaptability or versatility
If the coolant flow rate varies, then the cooling performance is optimized for different operating conditions, but the measurement precision deteriorates due to time lag variations
Solution Approach 1:
The patent employs dynamic gain values that change based on the coolant flow rate. Instead of using a fixed gain, the system adjusts the gain dynamically according to the actual flow conditions, allowing accurate temperature estimation across varying operating conditions. The control unit modifies the gain parameter in real-time to match the current thermal response characteristics of the system
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
The system accurately estimates coolant temperature, reducing time lag and improving control precision by using a gain map to adjust for variations in coolant flow rates, effectively addressing the indirect measurement challenges.
Implementation Method 1
The temperature sensor is attached to the casing so as not to contact the coolant directly. The temperature sensor is configured to measure a temperature of the casing
Implementation Method 2
The time constant is obtained when a transfer function of heat transferred from the coolant to the temperature sensor is modeled as a first order lag system
Data Source
AI summary
A cooler includes an estimator. The estimator is configured to estimate a coolant temperature from a measurement value of the temperature sensor. The estimator is configured to determine a difference by subtracting an immediately preceding measurement value from a current measurement value, determine a correction value from the difference, and output an estimated value of the coolant temperature. The estimated value is obtained by adding the correction value to the current measurement value. The correction value is obtained by multiplying a gain by the difference. The gain is determined from a time constant, the gain is determined according to a flow rate of the coolant. The time constant is obtained when a transfer function of heat transferred from the coolant to the temperature sensor is modeled as a first order lag system.