In the automotive industry, brazed aluminium heat exchangers represent nearly 100 per cent of the market today and the demand for heat exchanger material is strongly linked to global vehicle production. The number of heat exchangers per vehicle tends to increase in line with requirements for improved performance and enhanced functionality.
A number of unique heat exchangers are developed for each new vehicle platform. This work is carried out in close collaboration with the customers to ensure that the final product has the right charactertistics. Advanced requirements in respect of the products’ characteristics, particularly in terms of energy efficiency, means that aluminium brazing technology is clearly dominant in the heat exchanger industry today. Increased cost efficiency, reduced weight and more efficient heat exchangers have been the driving forces.
The inside story
Modern light vehicles typically contain up to ten different heat exchangers, sometimes more. In recent years, the number of heat exchangers per vehicle has increased, as engines have become more advanced, and environmental requirements and passenger comfort demands have grown. In electric vehicles there is a strong need for highly efficient heat exchangers for the thermal management of batteries. Plug-in hybrid electric vehicles have the largest need for heat exchangers – for cooling of both batteries and combustion engine, as well as heat exchangers for transmission oil and engine oil, air conditioning systems, and heaters. Today, Gränges is a world leader in heat exchanger materials, and around 50 per cent of sales are to customers in the automotive industry.
The charge air cooler cools the charged air after it has been compressed by, for instance, an exhaust gas-driven turbo charger. Charge air coolers are either air-cooled or water-cooled. The charge air cooler operates under high temperature and pressure conditions, resulting in material requirements for sufficient strength at elevated temperatures. Typical tube designs are large rectangular welded tubes, with inserts or extruded tubes with internal webs.
The condenser is part of the air conditioning system, and most often positioned in front of the radiator. The condenser cools the high-temperature, high-pressure gas refrigerant sent from the compressor and condenses it into liquid refrigerant, so enabling the air conditioning system to emit the heat absorbed by the evaporator. The most common design is the parallel flow condenser with extruded multiport tubes. Over recent years, alternatives with folded tube design have become common. The downgauging trend places very high demands on the clad fin when it comes to sag-resistance and strength. As well as this, the trend towards more folded tubes increases the demands on brazeability for this component.
The evaporator is part of the air conditioner system, and positioned inside the vehicle to absorb heat from the compartment. Typical design is either a drawn cup plate design or a flat tube design made from extruded micro channel tubes. Further enhancement and size reduction of the evaporator has led to the introduction of a folded tube design. Reducing the weight and size of the unit drives the development of thinner material with higher strength and excellent corrosion resistance and brazing performance.
The heater provides the interior of the car with heat transferred from the hot engine coolant in the radiator system. The heater core design has many similarities with the radiator and is typically made of a tube and fin design where the tubes are either welded or folded. A strong downgauging trend has been ongoing for heaters for many years, increasing demands on the corrosion performance and brazeability. The corrosion-resistant alloy system used in heaters consists, in many cases, of a long-life tube alloy and a zinc containing fin, where the fin protects the tube via galvanic action.
Oil coolers for cooling of engine oil, transmissions oil, power steering oils, etc, come in many different designs. Due to service conditions with high pressure and temperatures, the main material requirements are strength, corrosion resistance, and brazeability. Depending on performance needs and the positioning of the coil cooler, it can either be an air-cooled heat exchanger or a coolant-based heat exchanger.
The radiator lowers the temperature of the coolant passing through the engine block, to keep the temperature of the engine at the desired level. The radiator core is typically made of a tube and fin design, where the tubes are either welded or folded. A strong downgauging trend has been ongoing for radiators for many years, increasing demands on the corrosion performance, brazeability, and fatigue strength. The corrosion-resistant alloy system used in radiators consists, in many cases, of a long-life tube alloy and a zinc containing fin, where the fin protects the tube via galvanic action.