Regenerative heat exchanger
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Solution Overview
Problem
Conventional regenerative heat exchangers for vehicles with idling-stop systems have a short duration of low blow-off air temperature due to early melting of the regenerative material, which affects occupant comfort.
Innovation Solution
A regenerative heat exchanger design where the thermal resistance between the regenerative material on the upstream side and air is greater than on the downstream side, delaying the melting of the regenerative material to maintain a low temperature for a longer period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the regenerative material is placed in the air passage without differential thermal resistance design, then the heat exchange area is maximized, but the regenerative material melts early reducing the low temperature duration
Solution Approach 1:
The air passage fin is designed with different thermal resistance characteristics at different locations: the upstream side has larger thermal resistance while the downstream side has smaller thermal resistance. This local differentiation controls the heat transfer rate at each position, delaying melting on the upstream side and maintaining low temperature for longer duration.
Solution Approach 2:
The air passage fin structure is made asymmetric with respect to thermal resistance distribution along the air flow direction. The upstream portion and downstream portion have intentionally different thermal resistance values, creating an asymmetric heat transfer pattern that synchronizes melting timing and extends the effective cooling period.
2Duration of action of moving object
If the thermal resistance on the upstream side is increased, then the melting timing is delayed, but the heat exchange efficiency on the upstream side is reduced
Solution Approach 1:
Different thermal resistance values are assigned to different locations of the air passage fin based on local requirements. The upstream side uses higher thermal resistance to delay melting and extend duration, while the downstream side uses lower thermal resistance to maintain heat exchange efficiency, achieving optimal performance at each location.
Solution Approach 2:
The thermal resistance is optimized to provide just enough delay in melting timing without completely blocking heat transfer. The upstream side's increased thermal resistance is calibrated to delay melting to the optimal moment while still allowing sufficient heat exchange to occur, avoiding excessive resistance that would completely inhibit heat transfer.
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
Extends the time period during which the blow-off air temperature remains low, enhancing occupant comfort by synchronizing the melting of regenerative material on both sides, thus maintaining the low temperature feeling for a longer duration.
Implementation Method 1
a regenerator having a regenerative material that stores cold heat of the refrigerant by exchanging heat with the refrigerant flowing through the refrigerant pipe
Implementation Method 2
the air passage fin being thermally connected with the regenerator directly or through the refrigerant pipe
Implementation Method 3
the regenerative material starts melting when the blow-off air temperature exceeds the melting point of the regenerative material
Data Source
AI summary
A regenerative heat exchanger includes a refrigerant pipe, a regenerator, and an air passage fin. The air passage fin is disposed in an air passage defined outside of the refrigerant pipe and the regenerator, and is thermally connected with the regenerator directly or through the refrigerant pipe. At least one of the regenerator and the air passage fin is configured such that a thermal resistance between a part of a regenerative material located on an upstream side and air flowing through the air passage becomes larger than a thermal resistance between a part of the regenerative material located on a downstream side and air flowing through the air passage.