Compressor Inlet Pressure Estimation Using Evaporator Temperature Compensation
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Solution Overview
Problem
The existing refrigeration cycle systems face challenges in accurately estimating the inlet pressure of the compressor due to the response lag of thermistor detection values, which are delayed behind the actual refrigerant temperature, resulting in inaccurate pressure estimation in the evaporator and compressor.
Innovation Solution
A compressor inlet pressure estimation apparatus is developed, utilizing a temperature sensor to detect the surface temperature of the evaporator, with first-order lead and lag functions to estimate refrigerant temperature accurately, and subsequently the inlet pressure of the compressor, incorporating a second estimation method for enhanced accuracy during startup and steady-state conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermistor is used to detect refrigerant temperature in the evaporator, then the temperature can be detected, but the detection value lags behind the actual refrigerant temperature due to thermal capacity
Solution Approach 1:
The patent introduces an evaporator surface temperature sensor as an intermediary measurement point. Instead of directly measuring refrigerant temperature (which has thermal capacity lag), the system measures the evaporator surface temperature that more closely follows refrigerant temperature changes, then uses this as a basis for estimating actual refrigerant temperature through lead-lag compensation algorithms.
Solution Approach 2:
The patent changes the measurement parameter from direct refrigerant temperature to evaporator surface temperature. By measuring a different physical parameter (surface temperature vs. refrigerant temperature) that has a stronger correlation with the target parameter and less thermal inertia, the system achieves faster response while maintaining measurement accuracy through mathematical compensation.
2Speed
If evaporator surface temperature is used to estimate refrigerant temperature, then response speed improves, but estimation accuracy may be affected by thermal dynamics
Solution Approach 1:
The patent implements feedback through lead-lag compensation algorithms that continuously adjust the temperature estimation based on the relationship between evaporator surface temperature and actual refrigerant temperature. The system uses the measured surface temperature as feedback input and applies mathematical models to compensate for thermal dynamics, ensuring accurate refrigerant temperature estimation while maintaining fast response.
3Device complexity
If a single temperature estimation method is used, then the system is simple, but accuracy is insufficient during both startup and steady-state conditions
Solution Approach 1:
The patent applies dynamics by switching between different estimation methods based on operating conditions. During startup, when thermal dynamics are significant, one estimation method is used; during steady-state operation, another method provides higher accuracy. This dynamic adaptation allows the system to maintain optimal accuracy across different operating phases without excessive complexity.
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 enables precise estimation of the compressor inlet pressure by improving the accuracy of temperature determination and pressure estimation, ensuring reliable operation of the refrigeration cycle system.
Implementation Method 1
a temperature sensor (13) for detecting the surface temperature of an evaporator
Implementation Method 2
the function is the first-order lead function for estimating the refrigerant temperature in the evaporator based on the change rate of the surface temperature of the evaporator
Implementation Method 3
a pressure estimation means (S180) for estimating the refrigerant inlet pressure of the compressor based on the refrigerant temperature estimated by the first refrigerant temperature estimation means
Data Source
AI summary
A compressor inlet pressure estimation apparatus for a refrigeration cycle system is disclosed. An electronic control unit 14 uses Tefin_lag(N) as an actual corrected temperature Tefin_AD(N) during a period Tp1 included in the timing t1 to t2. During a period Tp2 included in the timing t1 to t2, Tefin_fwd(N) is used as the actual corrected temperature Tefin_AD(N). Thus, a highly accurate corrected temperature Tefin_AD(N) can be determined over the on period (t1 to t2) of a compressor 2. In addition, Tefin_fwd(N) is used as the actual corrected temperature Tefin_AD(N) during the off period (t2 to 3) of the compressor 2. As a result, a highly accurate corrected temperature Tefin_AD(N) can be determined over the whole period including the on and off periods of the compressor 2. In this way, a highly accurate estimated value Ps_es(N) of the refrigerant inlet pressure of the compressor 2 can be determined.