GB2326932A

GB2326932A - Heat exchanger with electric heater

Info

Publication number: GB2326932A
Application number: GB9713586A
Authority: GB
Inventors: Pierre Bugeja
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1997-06-30
Filing date: 1997-06-30
Publication date: 1999-01-06
Also published as: GB9713586D0

Description

HEAT EXCHANGER Technical Field The present invention relates to a heat exchanger, and more particularly to a heat exchanger for heating the passenger compartment of a motor vehicle.

Background of the Invention It is normal practice to pass the coolant fluid from an engine of a motor vehicle through a heat exchanger in order to provide heating for the passenger compartment of the motor vehicle. However, with the advent of more efficient engines, the coolant fluid is taking a considerable time (from initial start) to reach temperatures which are high enough to provide heating for the passenger compartment. It has been proposed to supplement the heating of the coolant fluid by providing direct heating for the fluid. Such supplement heating systems include electrically operated heaters mounted on the engine or positioned in the coolant fluid line to the heat exchanger in the engine compartment of the motor vehicle. However, these systems are inefficient as a large amount of the heat introduced into the coolant fluid is dissipated before the coolant fluid reaches the heat exchanger. Further, these systems induce a coolant side pressure drop which results in lower coolant flow which, in turn, leads to an augmented temperature variation across the heat exchanger (of the U-flow type).

Summarv of the Invention It is an object of the present invention to overcome one or more of the above mentioned disadvantages.

A heat exchanger in accordance with the present invention comprises an inlet tank; an outlet tank; tubes fluidly connecting the inlet tank to the outlet tank, the tubes extending substantially parallel to one another and being spaced apart; fins connecting adjacent tubes; an inlet pipe connected to the inlet tank; an outlet pipe connected to the outlet tank; and an electrically operable heater positioned in the inlet tank.

The present invention overcomes the problems and inefficiencies associated with the prior known systems by providing supplemental heating directly, at one or more locations, in the heat exchanger.

Further, with the present invention, it is possible to achieve controllability of left-to-right temperature spread in a U-flow heat exchange; enhanced performance under pre-determined conditions (such as under idling conditions of an engine in the motor vehicle); heating temperature control linearity; coolant flow distribution through the heat exchanger tubes; and management of pressure drop characteristics.

Brief Description of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawing in which the sole figure is a side view, partly in cross-section, of a heat exchanger in accordance with the present invention.

Description of the Preferred Embodlment Referring to the drawing, the heat exchanger 10 in accordance with the present invention comprises an inlet tank 12; an outlet tank 14; a return tank 16; and a number of tubes 18 which provide fluid flow paths between the inlet tank and the return tank, and between the return tank and the outlet tank. The tubes 18 extend substantially parallel to one another and are spaced apart. Fins 20 are connected between the tubes 18 and are such as to allow the transfer of heat from the heat exchanger 10 to air as it passes across the fins. The inlet tank 12 and the outlet tank 14 are positioned adjacent one another at one end 22 of the heat exchanger 10. The return tank 16 is positioned at the other end 24 of the heat exchanger 10. An inlet pipe 26 is connected to the inlet tank 12 and an outlet pipe 28 is connected to the outlet tank 14. The heat exchanger 10 can be positioned in the passenger compartment (not shown) of a motor vehicle. The inlet pipe 26 receives coolant fluid from the engine (not shown) of the motor vehicle. The coolant fluid passes through the inlet tank 12 and some of the tubes 18 to the return tank 16, and then flows through the other tubes to the outlet tank 14. The coolant fluid then returns to the engine through the outlet pipe 28.

In accordance with the present invention, supplemental heating is provided for the coolant fluid in the heat exchanger 10 by way an electrically operable heater 30, such as a glow plug, which is positioned in the inlet tank 12. Preferably, one or more electrically operable heaters 32 are additionally positioned in the return tank 16. The heaters 30,32 are connected to a control unit 34 which monitors the status of the vehicle ignition switch 36, and preferably the vehicle's electrical balance, and which actuates the heaters for a predetermined time when the ignition switch is initially actuated.

Alternatively, or additionally, the control unit 34 may be operated as a function of passenger compartment temperature and/or coolant fluid temperature and/or treated air temperature by connecting the control unit to temperature sensors at appropriate locations within the motor vehicle. The heaters 30,32 may also be manually operated by the vehicle operator or a passenger in the vehicle.

The present invention therefore provides supplemental heating for the heater exchanger which provides heat for the passenger compartment of a motor vehicle. As the heat is introduced to the coolant fluid as it enters the heat exchanger 10, and also preferably as it passes through the heat exchanger, the problem of heat dissipation from the coolant fluid before it reaches the heat exchanger is overcome. Further, the risk of a temperature variation across the heat exchanger due to decreased coolant fluid flow is limited and may be managed using a suitable control unit. The present invention therefore provides a more efficient way of achieving supplemental heating for the heat exchanger and provides a means of effectively controlling the performance of the heat exchanger.

Claims

1. A heater exchanger comprising an inlet tank; an outlet tank; tubes fluidly connecting the inlet tank to the outlet tank, the tubes extending substantially parallel to one another and being spaced apart; fins connecting adjacent tubes; an inlet pipe connected to the inlet tank; an outlet pipe connected to the outlet tank; and an electrically operable heater positioned in the inlet tank.

2. A heat exchanger as claimed in Claim 1, further comprising a return tank; wherein the inlet tank and the outlet tank are positioned adjacent one another at one end of the heat exchanger and the return tank is positioned at the other end of the heat exchanger, some of the tubes fluidly connecting the inlet tank to the return tank, and the other tubes fluidly connecting the return tank to the outlet tank.

3. A heat exchanger as claimed in Claim 2, wherein one or more electrically operable heaters are positioned in the return tank.

4. A heat exchanger as claimed in anyone of the preceding Claims, wherein the or each electrically operable heater is a glow plug.

5. A heat exchanger as claimed in anyone of the preceding Claims, further comprising control means connected to the or each electrically operable heater for controlling the operation of the or each electrically operable heater dependent on one or more conditions monitored by the control unit.

6. A heat exchanger as claimed in Claim 5, wherein one of the monitored conditions is the status of an ignition switch in a motor vehicle within which the heat exchanger is positioned.

7. A heat exchanger as claimed in Claim 5 or Claim 6, wherein one of the monitored conditions is the temperature of coolant fluid passing through the heat exchanger.

8. A heat exchanger substantially as herein described with reference to, and as shown in, the accompanying drawing.