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Technical Paper

Double-pipe Internal Heat Exchanger for Efficiency Improvement in Front Automotive Air Conditioning System

In automotive air conditioning, balancing comfort and fuel efficiency is very important. Vehicle cooling performance improvements during initial cool down has reached a limit in recent years, especially in very hot regions. We have addressed this issue by developing a unique double-pipe internal heat exchanger. In the main discourse, we first clarify the concept of the internal heat exchanger system (IHE) using the temperature difference between the high and low pressure pipes in the refrigeration cycle, and propose the application of an efficient internal heat exchanger. This unique double-pipe internal heat exchanger can easily be manufactured by inserting the inner pipe into the outer pipe and by fixing the pipes at both ends. The length of the IHE is 400mm. This double-pipe internal heat exchanger can increase cooling performance by 5-12% at the equivalent power consumption levels in the same space as a conventional front air conditioner system.
Technical Paper

Improvement in the Brazeability of Aluminum Clad Thinner Fin for Automotive Heat Exchanger

Through the years, aluminum automotive heat exchangers have been developed in order to have a high performance and a light weight. Therefore, the thickness of the aluminum sheets for the application has been reduced. As the brazeability declines with the reduction in thickness, fins having a thickness under 80μm may be difficult to secure a good brazeability. Therefore, we studied the brazeability to determine the limit of thickness using clad fins from 40 to 80μm. The fillet volume formed at the joints of the fin and tube decreased with the decreasing fin thickness and the Si content in both the filler metals and the core alloys. The suitable range of Si content in the filler metals and the core alloys to obtain a good brazeability decreased with the decreasing fin thickness. When the fins were thinner than the critical values, it was impossible to have a good brazeability.
Technical Paper

Development of a Cooling Module Containing a Radiator and a Condenser Part 1: Product Design

In conventional automobile designs, a radiator for cooling the engine and a condenser for condensing the air-conditioner refrigerant are typically configured independently of each other; they are usually mounted in series in the front of the engine compartment so that they will receive sufficient air flow while the vehicle is running. We have developed a smaller and higher performance cooling module by integrating these two heat exchangers into one unit. (Fig 1) For the heat dissipation fin, we have employed an integral fin construction equipped with an insulating slit, resulting in effective prevention of thermal conduction from the higher temperature radiator side, to the condenser side. We also succeeded in improving heat dissipation performance by making effective use of the connection part of the integral fin.
Technical Paper

Development of Quad-layer Clad Brazing Sheet for Drawn Cup Type Evaporator: Part 2

We have achieved significant weight reduction for the MS (Multi-Tank Super Slim Structure) Evaporator (1)currently in production at DENSO CORPORATION. The evaporator of HVAC unit, located in the instrument panel, is a component of the aluminum heat exchanger used in automotive air conditioners. The new evaporator uses thinner quad-layer sheet material, thanks to optimization of the electrical potential among its outer filler metal, intermediate anodic layer and core. The evaporator is thus lighter than conventional evaporators, but retains equivalent corrosion resistance.
Technical Paper

Development of Quad-layer Clad Brazing Sheet for Drawn Cup Type Evaporators: Part 1

Having a light weight, a good heat conductivity and a good brazability, aluminum alloy is widely used for automotive heat exchanger systems. The major problem with Aluminum is perforation of the tube by pitting corrosion and corrosion protection is necessary in the field. In radiator and condenser systems using the the Nocolok brazing process given good corrosion resistance using cathodic protection with sacrificial anode made of Zn-sprayed onto tube or low corrosion potential fins etc. On the other hand, in drawn-cup type evaporators, that are fabricated from brazing sheet tubes in vacuum brazing method and then covered low electro-conductive drain water film in operation, the effect of cathodic protection by the anode fin is limited to a very small area. Therefore, this has been studied to improve self-corrosion resistance of the core in the brazing sheet tube.
Technical Paper

Exhaust Gas Sensor with High Water Splash Resistant Layer for Lower Emission

Increasingly stringent regulations call for the reduction of emissions at engine startup to purify exhaust gas and reduce the amount of CO2 emitted. Air-fuel ratio (A/F) sensors detect the composition of exhaust gas and provide feedback to control the fuel injection quantity in order to ensure the optimal functioning of the catalytic converter. Reducing the time needed to obtain feedback control and enabling the restriction-free installation of A/F sensors can help meet regulations. Conventional sensors do not activate feedback control immediately after engine startup as the combination of high temperatures and splashes of condensed water in the exhaust pipe can cause thermal shock to the sensor element. Moreover, sensors need to be installed near the engine to increase the catalyst reaction efficiency. This increases the possibility of water splash from the condensed water in the catalyst.