Bulletproof cooling system
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All air in front of the radiator cradle is positive flow, air after the radiator cradle is negative flow in a driving automobile. In order for that arrangement to continue, air must be evacuated from the engine compartment. When the vehicle is at a standstill, the engine fan provides flow from positive to negative and cools the engine compartment. The fan should have the ability to push/pull enough air to keep the temperature within operating range of 160º to 210º. | All air in front of the radiator cradle is positive flow, air after the radiator cradle is negative flow in a driving automobile. In order for that arrangement to continue, air must be evacuated from the engine compartment. When the vehicle is at a standstill, the engine fan provides flow from positive to negative and cools the engine compartment. The fan should have the ability to push/pull enough air to keep the temperature within operating range of 160º to 210º. | ||
| − | If you are at the drags and need to cool down between rounds, run your electric water pump and fan along with a portable squirrel cage fan to bring down the temperature. On the return road turn the heater and | + | If you are at the drags and need to cool down between rounds, run your electric water pump and fan along with a portable squirrel cage fan to bring down the temperature. On the return road turn the heater and fan on high if so equipped. |
==Water pumps: electric vs. mechanical== | ==Water pumps: electric vs. mechanical== | ||
| − | Electric water pumps are constant flow pumps that push | + | Electric water pumps are constant flow pumps that push ‘X’ amount of gallons of water per minute, no matter what the rpm of the engine is. |
| − | Mechanical water pumps are variable speed pumps which have decreased flow at idle and increased flow at higher speeds | + | Mechanical water pumps are variable speed pumps which have decreased flow at idle and increased flow at higher speeds within their limitations. The limitations are mainly RPM induced cavitation. Mechanical pumps will only operate while the engine is running, but with electric pumps, operation is user-selectable. |
On a SBC for instance, the coolant flow of the OEM mechanical water pump is around 10-12 gall./min. per 1000 RPM. | On a SBC for instance, the coolant flow of the OEM mechanical water pump is around 10-12 gall./min. per 1000 RPM. | ||
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==Serpentine cross-flow radiators== | ==Serpentine cross-flow radiators== | ||
| − | Most cars from 1960 and up used cross flow radiators. One of the reasons was a lower hoodline, and two, more cooling area was required to cool the larger engines. Cross flow radiators had a tank with an inlet/outlet placed on either side. The water entered on one side and passed through the core of the rad, was cooled by the air flow and the heat escaped through convection to the outside air. Engineers found that the longer the liquid was exposed to the cooling flow of air through the radiator core, the more heat could be extracted from the flowing water. They slowed down the water travel by increasing the size of the water pump pulleys, but that had its limitations. They also added more rows of core, but that too had limitations. Road course racers in 1969 found a way to keep cooling to a simple easy form. To do this, they pulled the tanks off the radiators that they were using and placed baffle plates in the tank covers. The baffles were placed so as to divide the radiator core section into three distinct areas. Water would enter the upper radiator inlet on the right side and would flow across the top section of the radiator to the left side, a baffle plate located 2/ | + | Most cars from 1960 and up used cross flow radiators. One of the reasons was a lower hoodline, and two, more cooling area was required to cool the larger engines. Cross flow radiators had a tank with an inlet/outlet placed on either side. The water entered on one side and passed through the core of the rad, was cooled by the air flow and the heat escaped through convection to the outside air. Engineers found that the longer the liquid was exposed to the cooling flow of air through the radiator core, the more heat could be extracted from the flowing water. They slowed down the water travel by increasing the size of the water pump pulleys, but that had its limitations. They also added more rows of core, but that too had limitations. Road course racers in 1969 found a way to keep cooling to a simple easy form. To do this, they pulled the tanks off the radiators that they were using and placed baffle plates in the tank covers. The baffles were placed so as to divide the radiator core section into three distinct areas. Water would enter the upper radiator inlet on the right side and would flow across the top section of the radiator to the left side, a baffle plate located 2/3rds. of the way down the tank caused the coolant to flow across the radiator to the right side to the right radiator tank. The coolant couldn't rise upwards because a baffle plate located 1/3rd. of the way down stopped it and forced it to head down lower in the right tank, where it again was drawn across the radiator core to the lower left tank outlet and out to the engine. This serpentine course that the coolant took allowed the coolant to be cooled THREE TIMES by the cooling air flow coming through the core area. "Excellent idea!" you say, “Why don't they do that to all cars today?” In a closed course environment, the theory works, but in real everyday life the average auto would never warm up to operating temperature during the daily commute. |
Disagree, The Land Rover Discovery 300TDi (turbo diesel) had a crossflow radiator with the pipes at the same side. Allegedly some radiators were faulty insofar as the baffle was not installed correctly so the water could go from input to output without going through the core. | Disagree, The Land Rover Discovery 300TDi (turbo diesel) had a crossflow radiator with the pipes at the same side. Allegedly some radiators were faulty insofar as the baffle was not installed correctly so the water could go from input to output without going through the core. | ||
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The automotive radiator is essentially just another name for a heat exchanger, whereby combustion temperatures are transferred to the cooling system of the engine block and taken outside the block via flexible radiator hoses to be exposed to the cooling force of air through the radiator core, thus reducing the temperature of the coolant before returning it to the engine block. There are two restrictions in the system. One is the thermostat, which restricts flow and holds heat in the engine until warmed up, and the other is the radiator core tubes. The radiator tubes have to be of sufficient size so as to allow the coolant to flow through in an unrestricted manner, but also able to 'scrub off' BTU's or heat; which is based on the shape of the tube and the convection of heat away from the coolant to the outside air. A wide flat tube will expose more surface area to the outside flow of air than a narrow tube. The reason for this is more surface area is exposed to cooling. Look at the pictures located below and see why that is. | The automotive radiator is essentially just another name for a heat exchanger, whereby combustion temperatures are transferred to the cooling system of the engine block and taken outside the block via flexible radiator hoses to be exposed to the cooling force of air through the radiator core, thus reducing the temperature of the coolant before returning it to the engine block. There are two restrictions in the system. One is the thermostat, which restricts flow and holds heat in the engine until warmed up, and the other is the radiator core tubes. The radiator tubes have to be of sufficient size so as to allow the coolant to flow through in an unrestricted manner, but also able to 'scrub off' BTU's or heat; which is based on the shape of the tube and the convection of heat away from the coolant to the outside air. A wide flat tube will expose more surface area to the outside flow of air than a narrow tube. The reason for this is more surface area is exposed to cooling. Look at the pictures located below and see why that is. | ||
| − | One problem with copper | + | One problem with a copper radiator is corrosion of the fins from between the coolant tubes. If left unchecked, this will eventually leave just the tubes. This corrosion can be worse in inclement climes. |
[[Image:Tube_sizes.gif|frame|Tube sizes.]] [[Image:Alum_vs_copper_brass.gif|frame. Aluminum vs. copper/brass]] | [[Image:Tube_sizes.gif|frame|Tube sizes.]] [[Image:Alum_vs_copper_brass.gif|frame. Aluminum vs. copper/brass]] | ||
==Aluminum radiators== | ==Aluminum radiators== | ||
| − | If you are designing/redesigning a cooling system for your car, the utilization of the aluminum radiator is the best overall product on the market for the dollar. This is not to say that the radiators made from copper and brass are not good, and if you have one that works, don't go out and change for the sake of change. But, the choice of aluminum media will outperform their copper counterparts quite easily even though copper is a better conductor of heat. What is a lesser conductor of heat (aluminum) makes up with more surface area available for heat exchange. A 1.25" two-row aluminum radiator will cool just about anything up to 450 | + | If you are designing/redesigning a cooling system for your car, the utilization of the aluminum radiator is the best overall product on the market for the dollar. This is not to say that the radiators made from copper and brass are not good, and if you have one that works, don't go out and change for the sake of change. But, the choice of aluminum media will outperform their copper counterparts quite easily even though copper is a better conductor of heat. What is a lesser conductor of heat (aluminum) makes up with more surface area available for heat exchange. A 1.25" two-row aluminum radiator will cool just about anything up to 450 HP. If designed correctly, it will outperform most 4 or 5 row copper brethren. Not only does aluminum offer a great deal more surface area for cooling, but also has a more rigid structure, making for a less likely leaky situation. Also to the credit of this technology and the fact that more modern cars are implementing aluminum, more and more vendors are competing in this product line making for very attractive pricing. |
===Sacrificial anode in aluminum radiators=== | ===Sacrificial anode in aluminum radiators=== | ||
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Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure. | Usually located within a metal or plastic housing where the upper radiator hose connects to the engine, most of today’s thermostats utilize the "reverse poppet" design, which opens against the flow of the coolant. Thermostats have a wax filled copper housing or cup called a "heat motor" that pushes the thermostat open against spring pressure. | ||
| − | As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within | + | As the engine's coolant warms up, the increase in heat causes the wax to melt and expand. The wax pushes against a piston inside a rubber boot. This forces the piston outward to open the thermostat. Within 3º or 4º F. of the thermostat preset/rated temperature which is usually marked on the thermostat, the thermostat begins to unseat so coolant can start to circulate between the engine and radiator. It continues to open until engine cooling requirements are satisfied. It is fully open about 15º-20º above its rated temperature. If the temperature of the circulating coolant begins to drop, the wax element contracts, allowing spring tension to close the thermostat, thus decreasing coolant flow through the radiator. |
On some applications, the thermostat performs an additional function. It closes off a bypass circuit inside the engine when it opens the radiator circuit. The bypass circuit circulates coolant inside the engine so that hot spots can’t form when the radiator circuit is closed. | On some applications, the thermostat performs an additional function. It closes off a bypass circuit inside the engine when it opens the radiator circuit. The bypass circuit circulates coolant inside the engine so that hot spots can’t form when the radiator circuit is closed. | ||
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