cooling system

A battery cold plate is a cold plate that removes heat from battery cells or battery modules. It must ensure a uniform temperature distribution because temperature differences influence ageing, performance and safety. The cooling channels must be designed so that all cell regions are supplied sufficiently. Besides thermal performance, sealing, crash safety, electrical insulation, weight and manufacturing are important.

A battery cooler removes heat from the battery cooling circuit. It can be designed as an air-to-coolant heat exchanger, chiller connection or another heat exchanger type. The goal is to keep the battery within a temperature window that supports power, fast charging, safety and lifetime. Not only average temperatures matter, but also temperature uniformity between cells and modules.

Battery cooling keeps battery cells within a safe and performant temperature range. It is decisive for fast charging capability, continuous power, lifetime, ageing and safety. In addition to maximum temperature, temperature uniformity between cells is especially important. Battery cooling can be implemented using cold plates, coolant circuits, chillers, air cooling or direct cooling methods.

A bypass is a flow path that routes part of the coolant around a component. It is often used to bypass the radiator during warm-up or to ensure minimum flow rates. Bypasses improve system controllability, but if poorly designed they can create unwanted short-circuit flows. In simulation, the bypass is important because it strongly influences temperature distribution, pressure loss and flow split.

A charge air cooler reduces the temperature of compressed intake air downstream of the compressor. Colder charge air has higher density and therefore improves cylinder filling. It can also reduce knock tendency and thermal loading. However, a charge air cooler also causes pressure loss, so cooling performance and flow resistance must be optimized together.

A chiller is a refrigerant-to-coolant heat exchanger. It uses the refrigerant circuit to actively cool a coolant circuit below ambient temperature or below the level achievable with a normal radiator. In electric vehicles, a chiller is often used for battery cooling, fast charging or high continuous power. Its design must consider cooling capacity, pressure loss, control, condensation and coupling with air conditioning and heat pump operation.

A cold plate is a component that absorbs heat through a flat contact surface and transfers it to a coolant. It is often used for battery cells, power electronics, inverters or other planar heat sources. Key factors are contact thermal resistance, channel geometry, temperature uniformity, pressure loss and manufacturability. A poorly designed cold plate can cause local hot spots even if total coolant flow is sufficient.

A condenser is a heat exchanger in the refrigerant circuit where the refrigerant rejects heat and changes from gas to liquid. In vehicles, it is often placed in front of or within the cooling module. Its performance affects air conditioning, battery cooling through the chiller and overall thermal management. Because the condenser influences airflow and pressure loss in the front-end, it must be considered together with radiators, fans and ducting.

Cooling describes the controlled removal of heat from components, fluids or systems. In vehicles and machines, it protects components from overheating and keeps them within a suitable temperature window. Good cooling considers not only maximum heat flow, but also temperature distribution, pressure loss, packaging, control and operating conditions. Especially in engines, batteries, power electronics and high-performance applications, cooling is a central design topic.

A cooling channel is a flow passage through which coolant is guided to absorb heat. It can be integrated into engine components, cold plates, power electronics, housings or additively manufactured parts. Geometry, cross-section, bends and roughness influence heat transfer and pressure loss. In CFD design, cooling channels are often checked for hot spot avoidance and uniform flow distribution.

A cooling circuit is a closed or partly closed fluid loop that transports heat from a source to a sink. The coolant absorbs heat at components and rejects it through radiators or heat exchangers. Important quantities include volume flow rate, pressure loss, temperature difference, pump power and heat transfer. Vehicles often have several coupled cooling circuits with different temperature levels.

Coolant is the fluid that absorbs and transports heat in the cooling system. In vehicles, a water-glycol mixture is often used because it transfers heat well and provides freeze protection. Coolant properties influence heat transfer, pressure loss, pump power, corrosion protection and electrical safety. For batteries and power electronics, additional requirements for conductivity, ageing and material compatibility may be relevant.

A coolant circuit transports heat using a liquid coolant through pipes, components and heat exchangers. It can use water-glycol mixtures, special fluids or other suitable media. The circuit must provide sufficient volume flow without causing unnecessarily high pumping losses. Deaeration, freeze protection, corrosion protection, sealing and temperature control are important practical design topics.

A coolant pump generates the volume flow in the cooling circuit. It must provide enough flow to remove heat from critical components. At the same time, it consumes power and can promote cavitation, noise or unnecessary pressure losses if poorly designed. In modern thermal management systems, the pump map is an important element for control, efficiency and transient temperature behaviour.

A coolant valve controls, blocks or distributes coolant flow between different paths. It can be used to connect or disconnect radiators, bypasses, batteries, cabin heating, chillers or engines selectively. In modern thermal management systems, valves play a central role in temperature control and energy efficiency. A poor valve strategy can cause hot spots, long warm-up times or unnecessary pump power.

Cylinder head cooling removes heat from one of the most thermally loaded engine components. Critical regions include exhaust valves, valve seats, spark plug, injector, combustion chamber roof and exhaust ports. Insufficient cooling can promote knock, pre-ignition, material fatigue or local hot spots. Especially in high power density engines, hydrogen engines and motorsport applications, cylinder head cooling is a central development area.

An electric coolant pump is driven electrically and independently of engine speed. This allows coolant flow to be controlled according to demand, even when the combustion engine is stopped or during electric operation. It is especially important for hybrid vehicles, electric vehicles, after-run cooling and precise thermal management. Its design must consider head, volume flow, efficiency, lifetime, noise and controllability.

Electric motor cooling removes heat from stator, windings, rotor, magnets, bearings and housing. Winding temperatures and magnet temperatures are especially critical because they influence power, efficiency and lifetime. Depending on power density, jacket cooling, oil cooling, direct cooling or housing cooling can be used. Good electric motor cooling enables high continuous power and prevents thermal derating.

Engine cooling keeps the combustion engine, cylinder head, engine block, oil and adjacent components within the allowed temperature range. It must remove high heat flows from the combustion chamber, exhaust region, friction and oil circuit. At the same time, it should not keep the engine unnecessarily cold because that can worsen efficiency, friction and emissions. Modern engine cooling is therefore a controlled thermal management problem, not only a maximum cooling capacity question.

An evaporator is a heat exchanger in the refrigerant circuit where the refrigerant absorbs heat and evaporates. In vehicles, it is classically used for cabin cooling. It can also be indirectly connected to other thermal functions through refrigerant circuit strategies. Its performance depends on airflow, refrigerant state, humidity, temperature difference and control.

Fuel cell cooling keeps the fuel cell stack within a narrow temperature window. Excessive temperatures can damage the membrane, catalyst and lifetime, while temperatures that are too low can reduce efficiency and disturb water management. Uniform stack temperature is especially important because local hot spots can overload individual cells. Cooling is closely linked to air supply, water management, cold start, load changes and system efficiency.

A heat exchanger transfers heat from one medium to another without necessarily mixing the media. Typical combinations are coolant-to-air, oil-to-coolant, refrigerant-to-coolant or air-to-air. Its design depends on heat flow, temperature difference, surface area, material, flow arrangement and pressure loss. In thermal management systems, heat exchangers are central coupling elements between different circuits.

A high-temperature circuit operates at a higher temperature level and is often used for combustion engines, cylinder heads, engine blocks or certain power components. It can reject heat efficiently to ambient because the temperature difference to the environment is relatively large. At the same time, materials, seals, coolant and control must be designed for high temperatures. In hybrid or complex vehicles, the high-temperature circuit is often coupled with low-temperature circuits and cabin heating.

A high-temperature radiator rejects heat from a high-temperature circuit to ambient air. It is typically used for combustion engines, engine blocks, cylinder heads or other components operating at higher temperature levels. Because coolant temperature is high, the temperature difference to ambient is larger, which supports heat rejection. Nevertheless, packaging, airflow management, fan operation and pressure loss must be designed carefully.

Inverter cooling removes heat from power semiconductors, circuit boards, DC link and housing. The inverter converts electrical energy between battery and electric motor and generates heat losses in the process. Excessive temperatures reduce efficiency, lifetime and allowable continuous power. Cooling must handle high local heat fluxes while ensuring electrical insulation, sealing, packaging and low pressure loss.

A low-temperature circuit operates at a lower temperature level than a conventional engine cooling circuit. It is often used for charge air cooling, battery, inverter, electric motor or sensitive electronics. Because the temperature difference to ambient is smaller, low-temperature circuits often require larger cooling surfaces, good airflow management or active support from the refrigerant circuit and chiller. Its design is especially important for electrical power, battery lifetime and reproducible performance.

A low-temperature radiator rejects heat from a low-temperature circuit to ambient air. It is often used for charge air cooling, battery, inverter or electric motor cooling. Because the temperature level is lower, the driving temperature difference to ambient is smaller. Therefore, good airflow management, sufficient cooling surface and low air-side and coolant-side pressure loss are especially important.

An oil cooler removes heat from engine oil, transmission oil or hydraulic oil. Oil provides not only lubrication, but also cooling for bearings, pistons, gears and friction contacts. Excessive oil temperature worsens viscosity, lubrication capability and lifetime. An oil cooler must therefore reject enough heat without causing excessive pressure loss or overly long warm-up times.

Piston cooling reduces piston temperature, especially at the piston crown and piston ring area. Oil jets are often used to cool the piston from below. Good piston cooling protects against overheating, knock risk, oil coking, ring land damage and material fatigue. At the same time, it influences oil temperature, friction, pumping effort and the engine’s overall heat balance.

Power electronics cooling removes heat from components such as inverters, DC-DC converters, power semiconductors, circuit boards and DC links. High local heat fluxes at IGBTs, MOSFETs or SiC semiconductors are especially critical. Cooling affects efficiency, continuous power capability, lifetime and thermal derating. In addition to cooling performance, electrical insulation, sealing, pressure loss, packaging and thermal cycling resistance are important design criteria.

A radiator is a heat exchanger that rejects heat from the coolant to ambient air. It typically consists of tubes, fins, tanks and connections. Its performance depends on air volume flow, coolant volume flow, temperature difference, fin geometry and pressure loss. In a vehicle, the radiator is closely linked to the fan, front-end, air ducting and aerodynamics.

Radiator is the standard English term for a coolant-to-air heat exchanger. It usually refers to a component that rejects coolant heat to ambient air. The term is widely used in international projects, motorsport, CAE and vehicle development. In German technical glossaries, it should be explained as a synonym for Kühler to avoid translation ambiguity.

Thermal management describes the overall control and distribution of heat in a technical system. It includes heat sources, heat sinks, coolant circuits, heat exchangers, pumps, valves, sensors and control strategies. The goal is not only cooling, but maintaining optimal temperatures for efficiency, lifetime, safety and performance. In modern vehicles, thermal management is especially complex because battery, electric motor, inverter, cabin, engine and aftertreatment have different temperature requirements.

A thermostat controls coolant flow depending on temperature. In a conventional setup, it opens the path to the radiator only after a defined coolant temperature is reached. This accelerates warm-up and brings the engine or system into the desired temperature range more quickly. Modern thermostats can be mechanical, electrically heated or fully electronically controlled.

Vehicle cooling includes all systems that reject heat from powertrain, battery, power electronics, cabin and auxiliary components to the environment. This includes radiators, fans, airflow management, coolant circuits, heat exchangers and control valves. Vehicle cooling is closely linked to aerodynamics, packaging, energy consumption, noise and driving profile. The key is that cooling must work not only at one operating point, but also in traffic, hill climbs, towing, track use or fast charging.

The water jacket is the cooling channel system in the engine block or cylinder head. It guides coolant around thermally loaded regions such as combustion chamber, valve seats, exhaust ports and cylinder liners. Its design influences component temperatures, knock tendency, distortion, durability and heat losses. Good water jacket flow avoids dead-water regions, local overheating and non-uniform temperature fields.