Diesel engine pre-heater

A diesel engine pre-heater is provided that is connected within the diesel engine's exhaust system in a manner that forces the hot exhaust gases to pass directly through an internal chamber. Additionally, coolant from the engine's cooling system is routed through an internal network of passages within the heat exchanger. As the coolant flows through this system, the heat from the exhaust is transferred to the coolant which is then routed back to the diesel engine. The heated coolant then transfers its heat to the cold engine as it circulates, thus, greatly decreasing the time required to bring the engine up to operating temperature. Some of the coolant heated by the heat exchanger is also routed to the heater core of the cab's heating system. This allows the cab's heater to provide warm air to the interior cab of a truck much more quickly than a standard heating system. Additionally, the heat exchanger is also used to heat the diesel fuel before it enters the engine. This is accomplished routing the fuel through a shell on the outside of the heat exchanger which effectively warms the fuel to a temperature which ensures that the fuel will not gel, thereby enabling the fuel to flow efficiently at all temperatures.

BACKGROUND OF THE INVENTION 
The present invention relates to an improvement in the manner in which a 
diesel engine is brought to operating temperature during cold weather. 
More specifically, to an "add on unit" that will use the heat naturally 
generated by the engine's exhaust system to speed up the warming of the 
engine, the cab heater system and the diesel fuel. The present invention 
greatly reduces warm up time, thereby minimizing the excessive wear and 
tear caused to such engines in cold weather. 
During cold winter months, especially in northern climates, when a diesel 
engine is first started it, may take a long period of time for the engine 
to reach operating temperature. This can be hard on the engine itself as 
it runs at a temperature lower than the ideal operating temperature. 
Further, an operator attempting to use the truck may find it difficult to 
defrost the windows as the heater core will typically not receive heat 
until the engine is up to operating temperature. This problem is also 
uncomfortable, as the cab may take a long period of time to reach a proper 
temperature. 
For a diesel engine to operate efficiently it must maintain an internal 
temperature of 175 degrees Fahrenheit. If the temperature falls below this 
point it allows for the accumulation of water and sulfur in the engine. 
When a diesel engine is left to idle in cold weather, the operating 
temperature often drops ten or more degrees below the 175 degree point, 
thus, resulting in the above-described situation. This condition dilutes 
the engine oil, which increases engine wear due to the lack of 
lubrication, and can cause the engine valves to stick, which results in 
higher maintenance costs during the life of the engine. 
Therefore, from the foregoing discussion it can be seen that it would be 
highly desirable to provide a method accelerating the process of bringing 
a diesel engine up to a proper operating temperature and of maintaining a 
diesel engine at a suitable temperature during cold weather idle periods. 
Additionally, to provide such a system that will allow the heater core to 
receive heated coolant rapidly to accelerate the cabs heater and window 
defrosting system. 
Additionally, it is desirable to provide such a system that may also be 
used to preheat the diesel fuel for increased mileage and optimal burn. 
The present invention addresses these problems by providing a diesel engine 
pre-heater that is attached to the exhaust line after the turbo charger on 
a diesel engine. This pre-heater is also connected the cooling system and 
fuel system of the engine. 
SUMMARY OF THE INVENTION 
Therefore, it is the primary objective of the present invention to provide 
a method of heating the coolant used in a diesel truck engine quickly 
during warm-up in cold weather conditions, thereby, greatly reducing the 
time it takes for such engines to reach operating temperatures. 
It is an additional objective of the present invention to provide heat to 
the truck's cab heater system by again quickly heating the diesel engine's 
coolant which is used as a heat source in said cab heaters. 
It is a further objective of the present invention of providing a means by 
which the diesel fuel used in such applications can be heated to help to 
avoid the gelling problems commonly encountered when using diesel fuel in 
cold weather conditions. 
These objectives are accomplished by the use of a heat exchanger that is 
connected within the diesel engine's exhaust system in a manner that 
forces the hot exhaust gases to pass directly through an internal chamber. 
Additionally, coolant from the engine's cooling system is routed through 
an internal network of passages within the heat exchanger. As the coolant 
flows through this system, the heat from the exhaust is transferred to the 
coolant which is then routed back to the diesel engine. The heated coolant 
then transfers its heat to the cold engine as it circulates, thus, greatly 
decreasing the time required to bring the engine up to operating 
temperature. 
Some of the coolant heated by the heat exchanger is also routed to the 
heater core of the cab's heating system. This allows the cab's heater to 
provide warm air to the interior cab of a truck much more quickly than a 
standard heating system. Additionally, the heat exchanger is also used to 
heat the diesel fuel before it enters the engine. This is accomplished by 
routing the fuel through a shell on the outside of the heat exchanger, 
which effectively warms the fuel to a temperature which ensures that the 
fuel will not gel, thereby enabling the fuel to flow efficiently at all 
temperatures. 
For a better understanding of the present invention reference should be 
made to the drawings and the description in which there are illustrated 
and described preferred embodiments of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, and more specifically to FIGS. 1 and 2, the 
diesel engine pre-heater 10 comprises a heat exchange box 12 that installs 
in the existing exhaust system 16 of a diesel engine 14 behind the turbo 
charger 18. This design channels the hot exhaust gases produced by the 
engine 14 through a chamber within the heat exchange box 12. After passing 
through the heat exchanger 12 the exhaust gases then are simply channeled 
back into the exhaust system 16 where they are discharged as in a normal 
system. 
Coolant from the diesel engine 14 is routed into the heat exchange box 12 
by means of the coolant line from the engine 30. Once the coolant enters 
the heat exchanger 12, it is circulated through it and then pass out into 
the control valve 20 situated on top of the heat exchanger 12. The control 
valve 20 directs the flow of coolant to the various components of the 
system depending on the temperature of the coolant. When the coolant is 
below 180 degrees Fahrenheit, the thermostat 22 located on the direct 
engine return line 28 remains closed and the heated coolant is directed to 
the heated return line 26 and the cab heater line 24. 
This system quickly supplies heated coolant to the diesel engine 14, which 
greatly decreases the time required to bring the diesel engine 14 to 
operating temperature, and the cab heater, which greatly reduces the time 
necessary to heat the cab of a truck. When the coolant reaches the 
temperature of 180 degrees Fahrenheit, the thermostat 22 will then open 
and allow coolant to pass directly back to the diesel engine 14. It is 
important to note that even when the thermostat 22 is in the open position 
coolant will still flow to the cab heater line 24 to supply the cab with 
heat. 
Additionally, diesel fuel is heated by the diesel engine pre-heater 10 by 
passing the fuel through the outer shell of heater exchange box 12. This 
is accomplished by attaching the fuel line 32 to the heater exchange box 
12 prior to its entering the diesel engine 14. This design ensures that 
the fuel will flow efficiently to the engine 14 by eliminating the problem 
of fuel gelling that so frequently occurs during the operation of diesel 
engines 14 in cold temperatures. 
The internal structure of the heat exchange box 12 is shown by FIGS. 3, 4 
and 5. The exhaust gases enter the heat exchange box 12 through the 
exhaust in port 34, to which the exhaust system 16 is attached, and enters 
the heat chamber 46. When in the heat chamber 46, the hot exhaust gases 
encircle the coolant extension tubes 50 and the coolant flow tubes 48. It 
is here that the heat from the exhaust gases is transferred to the 
coolant. Once passing through the heat chamber 46, the exhaust gases pass 
out the back of the heat exchange box 12 through the exhaust out port 36 
and continue in their normal path through the exhaust system 16. 
Coolant enters the heat exchange box 12 through the coolant shell in port 
42. Once it enters, the coolant passes through the coolant shell 60 (as 
illustrated by the coolant flow arrows 56 on the figures) which encloses 
the outer surface 64 of the heat chamber 46 and then passes through the 
flow tube inlet 58 to the coolant flow tube 48 within the heat chamber 46. 
After flowing through the coolant flow tubes 48, the now heated coolant 
passes out of the heat exchange box 12 through the coolant out port 44 
where it is diverted to the desired location of the cooling system by the 
control valve 22. 
The heat exchange box 12 also has constructed on its outer most surface a 
fuel heater shell 62 through which fuel for the diesel engine 14 is 
passed. The diesel fuel enters the fuel heater shell 62 through the fuel 
in port 38 where it travels along the fuel heater shell 62 (as indicated 
by the fuel flow arrows 66 on the diagrams) until it passes out the fuel 
out port 40 and return to the fuel line 32. 
Additionally, both the fuel heater shell 62 and the coolant shell 60 act as 
an external insulator for the heat exchange box 12 which limits external 
heat build up of the system. It is important to note the temperature of 
the diesel fuel passing through the heat exchange box is limited to 
approximately 90 degrees Fahrenheit (well below its flash point) because 
it is insulated from the great heat of the heat exchange box 12 by the 
coolant shell 60 and the fact that it passes relatively quickly through it 
as it travels to the diesel engine 14. 
The path that the coolant follows through the coolant flow tube 48 and the 
coolant extension tubes 50 is illustrated by FIGS. 6 and 7. As coolant 
enters the coolant flow tube 48 through the flow tube inlet 58, it is 
channeled through the flow tube and into a plurality of coolant extension 
tubes 50 by a series of flow diverters 52. These serve to block the flow 
of the coolant along the flow tube 48 and force it to enter the coolant 
extension tubes 50 through the coolant passages 54. The coolant extension 
tubes 50 are U-shaped passages which extend out from the flow tube 48 and 
channel the coolant around this U and back into the flow tube 48. This 
process is repeated three more times before the coolant exits the heat 
exchange box 12 through the coolant out port 44. The purpose of the 
coolant extension tubes 50 is to increase the surface area at which the 
coolant is in contact with the heat of the exhaust gases which greatly 
increases the efficiency of the heat exchanger 12 by optimizing the amount 
of heat passed to the coolant. 
An alternative embodiment of the present invention is illustrated in FIGS. 
8, 9 and 10. The octagonal heat exchange box 68 installs and operates in a 
typical diesel engine 14 in much the same manner as the heat exchange box 
12 as previously discussed. The exhaust system 16 of the diesel engine 14 
conducts the exhaust into the octagonal heat exchange box 68 through the 
exhaust in port 34 where it surrounds the octagonal coolant flow tube 70 
before returning to the exhaust system 16 through the exhaust out port 36 
at the rear of the octagonal heat exchange box 68. 
The octagonal heat exchange box 68 is also used to preheat diesel fuel by 
providing an octagonal fuel cell 72 located at the front of the octagonal 
heat exchange box 68. Unlike the corresponding feature of the previous 
embodiment, the octagonal fuel cell does not cover the entire outside a 
surface of the octagonal heat exchange box 68, but rather, it is a 
relatively narrow chamber that extends from the outer surface to the 
exhaust in port 34. This design provides enough heat to the fuel to ensure 
that it remains in a fluid, free flowing state even in the coldest 
weather. 
The internal structure and manner of operation of the octagonal heat 
exchange box 68 are illustrated in FIGS. 11 and 12. The outer surface of 
the octagonal heat exchange box 68 is made up of the octagonal heat shell 
74 which forms the enclosed heat chamber 48 into which the hot exhaust 
gases flow. The heat chamber 48 houses the octagonal coolant flow tube 70 
through which the diesel engine's 14 coolant fluid flows prior to being 
diverted to the desired points by the present invention. The surface area 
of the octagonal coolant flow tube 70 is maximized by having a plurality 
of flow tube heat exchange passages 76 that extend from the outside to 
inside surfaces of the coolant flow tube 70. As the exhaust gases 
circulate through the heat chamber 48 and the flow tube heat exchange 
passages 76, the heat that they contain is transferred to the coolant 
flowing through the octagonal coolant flow tube 70, thus, providing an 
effective way of heating the coolant during early engine warmup periods. 
The flow of the engine coolant and diesel fuel through the octagonal 
coolant flow tube 70 and the octagonal fuel cell 72 are illustrated in 
FIGS. 13 and 14. Engine coolant enters the octagonal coolant flow tube 70 
through the coolant in port 42 where it is diverted around the length of 
the flow tube 70 by the coolant flow diverter 52 (the direction of flow of 
the coolant is indicated by coolant flow directional arrow 56). After 
completing its passage through the octagonal coolant flow tube 68, the 
heated coolant again encounters the coolant flow diverter 52 which forces 
it into the coolant out port 44 where it reenters the original cooling 
system. 
The fuel is heated by the octagonal heat exchange box 68 in much the same 
manner. The fuel enters the octagonal fuel cell 72 where the flow is 
diverted by the fuel flow diverter 67 (the direction of flow of the fuel 
is indicated by the fuel flow arrow 66). While the fuel is in the 
octagonal fuel cell 72, it is heated by the fuel cell's 72 contact with 
the heat chamber 48 sufficiently to eliminate gelling problems typically 
encountered in cold weather conditions. After completing its passage 
through the fuel cell 72, the heated fuel is directed back to the original 
fuel system through the fuel out port 40 by the fuel flow diverter 67. 
Although the present invention has been described in considerable detail 
with reference to certain preferred versions thereof, other versions are 
possible. Therefore, the spirit and scope of the appended claims should 
not be limited to the description of the preferred versions contained 
herein.