Simultaneous cooling of three different media in one cooler!

Efficient cooling of mobile machines is becoming more and more important. Specialist application and engineering knowledge is required for the selection of coolers, to ensure that the optimum cooling system is chosen for each application. Amongst these systems are combined coolers which include cooling systems for various media being integrated in one compact system. Whether it's drives for construction machines, agricultural machines or industrial trucks, the power packs for these machines have become more and more compact. With exhaust emission regulations becoming stricter – Tier 4 is already fixed and will be followed by further steps – there is an increasing demand for auxiliary and processing systems such as particle filters and exhaust gas recirculation, while operating parameters have remained in a defined range. Thermo management is well-understood Thus, the temperature of the motor, the cooling water, the charge air and the motor oil are becoming areas of increased concern to the manufacturers of motors and mobile machines. For example: While it has previously only been necessary to make sure that a drive system does not exceed a defined temperature, an efficient and well-designed thermo management is also now required. That is why the corresponding power packs for cooling are becoming more and more important – apart from cooling the motor, gearbox oil, water and air; they are even taking over some extra functions such as cooling the oil of the hydraulic circle as we too. Various lines – various principles Typical cooling processes in the drives of mobile machines include air coolers, plate heat exchangers and tubular heat exchangers. The series MMC produced by KTR (illustration 1) can be applied to cool diesel engines and gas motors, used on construction machines, agricultural machines and stationary I.C. engines with a variety of applications: being used as a water cooler, the series MMC cools the cooling water; when used as an oil cooler, ensuring the cooling of hydraulic or gear oil; and as a charge air cooler, handling the cooling of the combustion air. As a result the MMC high-power cooling system meets with all demands on the temperature regulation of media, including application as fuel cooler! It goes without saying that such cooling systems, must be developed individually, taking into account the necessary cooling power and requirements of the customer. If several power packs for cooling are requested, they can be arranged either 'on series' or 'in parallel'. Depending on the application, the MMC coolers are equipped with fans which are driven either hydraulically or via a 12/24V or 230/400V electric motor. The hydraulic systems have the benefit of a higher efficiency, lower sound emission and a better adaptability to the different operating conditions on bigger machines. Regardless of the mode of drive, the latest types of fans are used ensuring optimum efficiency and quiet running. Important: Efficient fans Before selecting a fan, extensive investigations are made to find the optimum solution for the individual application. Elements considered are: measurements of the velocity of air, the distance between the cooler and the cooling grid, the position of the fan in relation to the cover, and the inflow and outflow. For the selection of the cooling system, KTR use their extensive knowledge gained from various applications in mobile power transmission as well as stationary and mobile hydraulics. Our selection programme considers the required power, potential dirt and the ambient conditions. Detailed tests are taken as the basis of our calculations; the simulation is performed by means of the simulation software Kuli and software tools being developed by the KTR engineers themselves. Continuous comparison of theory and practice Having installed the cooling system, measurements are taken from the motor and used to optimise the thermo management, serving as the basis for the calculation of subsequent projects. In this way, theory and practice of the development of cooling systems are compared and continually optimised. Cooling of oil: The user has the choice Since the power density of hydraulic systems in mobile machines is increasing and the quantity of the corresponding pressure fluid is to be as low as possible, for reason of weight and environmental protection, an efficient cooling of the hydraulic oil is most important. For such applications KTR offer various systems like, for example, the oil/air cooler series OAC (illustration 2), the plate heat exchangers type PHE (illustration 3) and the tubular heat exchangers series TAK. All products are subject to a strict programme of inspection and are tested and modified either by in-house processes or in cooperation with manufacturers, subcontractors and universities of applied sciences. An increasing amount of responsibility for the manufacturer of coolers The extensive selection tools and the cooperation with universities of applied sciences are becoming more and more important, since an increasing amount of responsibility is transferred to the manufacturer of the coolers as the supplier of complete systems. This means that the manufacturers of mobile machines follow the general trend of no longer purchasing components only, but acquire complete systems ready to install, leaving the responsibility of development to the subcontractor. This corresponds to a principle of cooperation which has already proven its worth in the automobile industry. At the same time, the topic of cooling is becoming more complex. Necessary cooling powers are increasing, along with the demands on the energy efficiency of auxiliary power packs. Meanwhile, additional facts, such as exhaust gas recirculation, have to be taken into account. New tasks arising from Tier 4 This subject will become particularly interesting once the exhaust step "Tier 4" comes into force, which will make cooling by AGR and EGR systems necessary in many cases. It is generally expected that 30 to 50 % more heat will be needed in the cooling water circle. The additional cooling power required will have to be installed in the existing or a nominally larger space. This requires an extensive know-how and a comprehensive knowledge both with mechanical designing, i. e. integrating the cooling system into the vehicle, and the thermal selection of the power packs for cooling. Project planning of the entire system requires the selection of cooler, fan and motor, where 3D- drawings and an extensive knowledge of components, installation situation and cooling power data are used. Depending on the machine type, worst cast scenarios of machines maybe necessary, with high loads, high ambient temperatures and heavy dirt considered. Having installed a prototype or testing system, all relevant parameters are tested by means of the latest measuring technology in various operating points. A final analysis is undertaken which confirms the optimum design and ensures the operating safety of the cooling system.