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A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins attached to the core tubes serve to increase surface area for heat transfer to air that is forced past them by a fan, thereby heating the passenger compartment.
The internal combustion engine in most cars and trucks is cooled by a water and antifreeze mixture that is circulated through the engine and radiator by a water pump to enable the radiator to give off engine heat to the atmosphere. Some of that coolant can be diverted through the heater core to give some engine heat to the cabin, or adjust the temperature of the conditioned air.
A heater core is a small radiator located under the dashboard of the vehicle, and it consists of conductive aluminium or brass tubing with cooling fins to increase surface area. Hot coolant passing through the heater core gives off heat before returning to the engine cooling circuit.
The squirrel cage fan of the vehicle's ventilation system forces air through the heater core to transfer heat from the coolant to the cabin air, which is directed into the vehicle through vents at various points.
Once the engine has warmed up, the coolant is kept at a more or less constant temperature by the thermostat. The temperature of the air entering the vehicle's interior can be controlled by using a valve limiting the amount of coolant that goes through the heater core. Another method is blocking off the heater core with a door, directing part (or all) of the incoming air around the heater core completely, so it does not get heated (or re-heated if the air conditioning compressor is active). Some cars use a combination of these systems.
Simpler systems allow the driver to control the valve or door directly (usually by means of a rotary knob, or a lever). More complicated systems use a combination of electromechanical actuators and thermistors to control the valve or doors to deliver air at a precise temperature value selected by the user.
Cars with dual climate function (allowing driver and passenger to each set a different temperature) may use a heater core split in two, where different amounts of coolant flow through the heater core on either side to obtain the desired heating.
In a car equipped with air conditioning, outside air, or cabin air if the recirculation flap has been set to close the external air passages, is first forced, often after being filtered by a cabin air filter, through the air conditioner's evaporator coil. This can be thought of as a heater core filled with very cold liquid that is undergoing a phase change to gas (the evaporation), a process which cools rather than heats the incoming air. In order to obtain the desired temperature, incoming air may first be cooled by the air conditioning and then heated again by the heater core. In a vehicle fitted with manual controls for the heater and air conditioning compressor, using both systems together will dehumidify the air in the cabin, as the evaporator coil removes moisture from the air due to condensation. This can result in increased air comfort levels inside the vehicle. Automatic temperature control systems can take the best course of action in regulating the compressor operation, amount of reheating and blower speed depending upon the external air temperature, the internal one and the cabin air temperature value or a rapid defrost effect requested by the user.
Because the heater core cools the heated coolant from the engine by transferring its heat to the cabin air, it can also act as an auxiliary radiator for the engine. If the radiator is working improperly, the operator may turn the heat on (together with the cabin blower fan placed on full speed, and with the windows opened) in the passenger cabin, resulting in a certain cooling effect on the overheated engine coolant. This idea only works to a certain degree, as the heater core is not large enough nor does it have enough cold air going through it to cool large amounts of coolant significantly.
The heater core is made up of small piping that has numerous bends. Clogging of the piping may occur if the coolant system is not flushed or if the coolant is not changed regularly. If clogging occurs the heater core will not work properly. If coolant flow is restricted, heating capacity will be reduced or even lost altogether if the heater core becomes blocked. Control valves may also clog or get stuck. Where a blend door is used instead of a control valve as a method of controlling the air's heating amount, the door itself or its control mechanism can become stuck due to thermal expansion. If the climate control unit is automatic, actuators can also fail.
Another possible problem is a leak in one of the connections to the heater core. This may first be noticeable by smell (ethylene glycol is widely used as coolant and has a sweet smell); it may also cause (somewhat greasy) fogging of the windshield above the windshield heater vent. Glycol may also leak directly into the car, causing wet upholstery or carpeting.
Electrolysis can cause excessive corrosion leading to the heater core rupturing. Coolant will spray directly into the passenger compartment followed with white coloured smoke, a significant driving hazard.
Because the heater core is usually located under the dashboard inside of the vehicle and is enclosed in the ventilation system's ducting, servicing it often requires disassembling a large part of the dashboard, which can be labour-intensive and therefore expensive.
Since the heater core relies on the coolant's heat to warm the cabin air up, it will not begin working until the engine's coolant warms up enough. This problem can be resolved by equipping the vehicle with an auxiliary heating system, which can either use electricity or burn the vehicle's fuel in order to rapidly bring the engine's coolant to operating temperatures.
Engines that do not have a water cooling system cannot heat the cabin via a heater core; one alternative is to guide air around the (very hot) engine exhaust manifold and then into the vehicle's interior. Temperature control is achieved by mixing with unheated outside air. Air-cooled Volkswagen engines use this method. Another example is the air-cooled Briggs & Stratton Vanguard, used in the ultra and microlight flight amateur construction scene. This method for cockpit heating is a simple option for the Spacek SD-1 Minisport and other homebuilt sportplanes. However, depending on the design, this can cause a safety issue where a leak in the exhaust system will begin to fill the passenger cabin with deadly fumes.
Car heat cores are also used for Do-It-Yourself projects, such as for cooling homemade liquid cooling systems for computers. [1]
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation as HVAC&R or HVACR, or "ventilation" is dropped, as in HACR.
A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics.
A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and relatively simple system. Watercraft can use water directly from the surrounding environment to cool their engines. For water-cooled engines on aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped through the engine to the surrounding atmosphere by a radiator.
A central heating system provides warmth to a number of spaces within a building from one main source of heat. It is a component of heating, ventilation, and air conditioning systems, which can both cool and warm interior spaces.
Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine compressor sections; low stage air is used during high power setting operation, and high stage air is used during descent and other low power setting operations. Bleed air from that system can be utilized for internal cooling of the engine, cross-starting another engine, engine and airframe anti-icing, cabin pressurization, pneumatic actuators, air-driven motors, pressurizing the hydraulic reservoir, and waste and water storage tanks. Some engine maintenance manuals refer to such systems as "customer bleed air".
A block heater is used in cold climates to warm an engine prior to starting. They are mostly used for car engines; however, they have also been used in aircraft engines.
In aeronautics, an environmental control system (ECS) of an aircraft is an essential component which provides air supply, thermal control and cabin pressurization for the crew and passengers. Additional functions include the cooling of avionics, smoke detection, and fire suppression.
An air cycle machine (ACM) is the refrigeration unit of the environmental control system (ECS) used in pressurized gas turbine-powered aircraft. Normally an aircraft has two or three of these ACM. Each ACM and its components are often referred as an air conditioning pack. The air cycle cooling process uses air instead of a phase changing material such as Freon in the gas cycle. No condensation or evaporation of a refrigerant is involved, and the cooled air output from the process is used directly for cabin ventilation or for cooling electronic equipment.
A bleed screw is a device used to create a temporary opening in an otherwise closed hydraulic system, which facilitates the removal of air or another substance from the system by way of pressure and density differences.
An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. Solar energy, burning a fossil fuel, waste heat from factories, and district heating systems are examples of heat sources that can be used. An absorption refrigerator uses two coolants: the first coolant performs evaporative cooling and then is absorbed into the second coolant; heat is needed to reset the two coolants to their initial states. Absorption refrigerators are commonly used in recreational vehicles (RVs), campers, and caravans because the heat required to power them can be provided by a propane fuel burner, by a low-voltage DC electric heater or by a mains-powered electric heater. Absorption refrigerators can also be used to air-condition buildings using the waste heat from a gas turbine or water heater in the building. Using waste heat from a gas turbine makes the turbine very efficient because it first produces electricity, then hot water, and finally, air-conditioning—trigeneration.
A defogger, demister, or defroster is a system to clear condensation and thaw frost from the windshield, backglass, or side windows of a motor vehicle. The rear window defroster was invented by German automobile engineer Heinz Kunert.
Economizers, or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, refrigeration, ventilating, and air conditioning (HVAC) may all use economizers. In simple terms, an economizer is a heat exchanger.
The Weather Eye was a trade name for a Nash Motors-designed fresh-air system for automobile passenger compartment heating, cooling, and ventilating. The Nash "All-Weather Eye" was the first automobile air conditioning system for the mass market. The use of the Weather Eye name for automobile passenger heating and air conditioning systems continued in American Motors Corporation (AMC) vehicles.
The wax thermostatic element was invented in 1934 by Sergius Vernet (1899–1968). Its principal application is in automotive thermostats used in the engine cooling system. The first applications in the plumbing and heating industries were in Sweden (1970) and in Switzerland (1971).
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that transmits heat from one location at a certain temperature to another location at a higher temperature. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink, or a "refrigerator" or “cooler” if the objective is to cool the heat source. The operating principles in both cases are the same; energy is used to move heat from a colder place to a warmer place.
Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plants or any similar use of such an engine.
Radiators and convectors are heat exchangers designed to transfer thermal energy from one medium to another for the purpose of space heating.
Automotive air conditioning systems use air conditioning to cool the air in a vehicle.
