US2173169A - Heat transfer apparatus - Google Patents

Description

Sept. 19, 1939. J ms 2,173,169

HEAT TRANSFER APPARATUS Filed Feb. 15, 1936 5 Sheets-Shet 1 3/ XNVENTQR H 3 4% Z5 *5 4 ATTORNEYS Sept. 19, 1939. J. M. JENKINS HEAT TRANSFER APPARATUS 5 Sheets-Sheet 2 Filed Feb. 15, .1936

' lNVENT Q- ATTORNEYS Sept. 19, 1939. J, M. JENKINS 7 HEAT TRANSFER APPARATUS Filed Feb. 15, 1936 5 Sheets-Sheet 3 Liz..

INVENTOR ATTORNEYJ Patented Sept. 19, 1939 "PATENT OFFICE HEAT TRANSFER APPARATUS James M. Jenkins, Philadelphia, Pa., assignor to Andale Company, Philadelphia, Pa., a corporation of Pennsylvania ApplicationFebruary 15, 1936, Serial No. 64,023

1 Claim.

This invention relates to heat transfer apparatus and is especially concerned with equipment adapted for use in connection with the heating or cooling of oil or similar liquid of a relatively 5 viscous nature and, broadly considered, it aims to improve the efllciency of heat transfer as well as to minimize or eliminate certain disadvantages incident to apparatus heretofore in use, as will further appear.

The invention is particularly applicable to the heating of oil, for which reason the accompanying disclosure will relate primarily to its usefulness in this field although, as will be apparent, certain features of the invention may be equally useful in cooling oil or a similar viscous liquid.

The improvements which I have developed are peculiarly applicable to the heating of rather small quantities of oil, preferably in the neighborhood of one to two gallons per minute and within a temperature range running up to approximately 180 F. or thereabouts, and the apparatus herein illustrated and described is primarily designed for this class of service. It is useful, for example, in heating small quantities 5 of lubricating oil in order to increase its fluidity for centrifuging, or for the heating of fuel oil for domestic oil burners, or for use in Diesel engines, etc.

In considering the objects and advantages of the invention as they appear hereinafter, it should be borne in mind that relatively viscous liquids, particularly oil, have a rather high"fi1m resistance, i. e., a resistance to the giving up or taking on of heat as compared with more fluid liquids such, for example, as water.

Among the objects of the invention, therefore, is the provision of. a heat transfer apparatus of the character described in which the resistance to heat transfer is markedly reduced by greatly 40 increasing the turbulence of the viscous liquid over the area where the heat transfer is taking place.

. It is also an object of the invention to indirectly heat oil by means of a relatively fluid medium, such as water, in which is immersed a heating unit, preferably electrical.

' A further object of the invention is to prevent carbonization of the oil on the heating surfaces and to make possible a heater in which the oil side can be readily cleaned.

Another object of the invention is to eliminate all fire hazard in a device of this kind, as well as to provide a heating unit which will prevent any overheating of the oil, in connection with 56 which latter Object it is a further aim of the invention to avoid any burning or overheating of the oil regardless of the quantity of oil which may be going through the heater or the slowness of its flow.

Another object of the invention is to provide a heater which will serve to clean the oil of foreign particles and dirt of one kind or another.

Somewhat more specifically stated, the invention contemplates the use of water or some other relatively fluid liquid as the heat transfer medium, which medium is heated directly by a heating element, preferably electrical.

How the foregoing objects and advantages are attained will be brought out more fully in connection with the following description referring to the accompanying drawings, in which Figure 1 is a vertical sectional view of a heat exchanger constructed in accordance with this invention, taken as indicated by the section line |l on Figure 2;

Figure 2 is also a. vertical sectional view, but taken approximately at right angles to the section of Figure 1;

Figure 3 is a top plan view of the equipment; and

Figure 4 is a horizontal sectional view taken as shown by the section line 4-4 on Figure 1.

The unit shown includes a shell 5 which may conveniently be of tubular shape and molded with lagging 6 for insulation purposes. A bottom end closure 1 and a top closure 8 define the end walls of a chamber adapted to receive the heat transfer medium, the upper level of which appears at W in Figure 1.

The heat transfer medium is heated preferably by an electrical heating element 9 which may conveniently project upwardly through the bottom closure 1. The heater may be in part surrounded by a baflle Ill serving to define a channel through which the medium circulates during operation. A vent H may be provided at the top of the chamber, and water may be introduced into the chamber by removal of the cap I! serving to close the upper end of a tube l3 preferably formed as a gauge glass. A thermostat 9a is provided for the purpose of shutting off the current should the temperature rise above a predetermined limit say, for example, 200 F.

The present embodiment also employs a float ll for controlling the current, which float is mounted for vertical movement as by stems l5 and IS, the stem l6 serving to actuate a switch H in the heating circuit for the element 9. The detailsof this switch form no part of the present invention per se, although it is mentioned that upon a drop in the water level and a consequent drop of the float I4, the switch I! is actuated to break the heating circuit. Thus the equip ment will not operate if the water level drops below a predetermined point.

It will be obvious that either the float alone or the thermostat alone or both together may be provided, and I do not Wish to be limited to any particular means for shutting off the current. If both devices are adopted they may be interrelated in such a way that the float exerts the primary control with the thermostat arranged to function only in case of a failure of the float.

An oil flow tube I8, preferably of copper, with its end portions projecting through the heads I and 8 and bent over, as shown, is positioned within the chamber so as to be surrounded by the water therein. The tube is provided with connection members 19 and 20, the former of which is provided with an inlet 2| and the latter with an outlet 22. The connection members are attached by bolts such as shown at Main Figure 3. Caps 23 serve to close the ends of the oil tube and may be tightened in position as by means of yokes 24 and hand screws 25.

Within the tube I 8 I position a core which may conveniently be built up on a rod 26 by alternately stacking a multiplicity of annular fins 21 and spacing washers 28. This core is centrally located in the tube l8 with slight clearance between the peripheral edges of the fins and the inside wall of the tube. The several fins and spacer members maybe tightened by means of nuts 29 threaded onto the ends of rod 26. Rod extensions 30 cooperate with suitable recesses formed on the inside faces of the end caps 23 in order to ensure proper positioning of the core.

in use the equipment is operated in substantially the following manner:

First, the chamber within the shell 5 is supplied with water, and this water is heated by means of the heater 9. Oil is then caused to flow from the inlet 2| to the outlet 22. This flow, of course, takes place around the edges of the fins 21, which are positioned in planes at an angle, preferably a right angle, to the general direction of flow and, therefore, set up intensive turbulence or eddying around the edges of the fins.

While I have found that indirect transfer of heat from the heater element 9 or equivalent device through the water or equivalent medium, to the oil is of advantage in improving heat transfer to a viscous liquid, it is pointed out that the present invention further contemplates the use of a means, such as the fins 21 within the tube l8, for creating a high degree of turbulence in the oil during the time it is passing in heat transfer relation with respect to the medium. I have found that this condition of turbulence is of great importance in securing the desired high rate of heat transfer, because a mere increase in velocity in flow does not accomplish the improvement effected in accordance with this invention.

In addition to the foregoing, tests have shown that the degree of turbulence preferably should pass a certain critical. value in order to fully attain the objects of this invention. In order to attain turbulence at or above the critical value,

the equipment may have to be modified in accordance with the pressure and the volume of oil a cleaning operation.

passed through the equipment per unit of time, although I have found that for a heater having a capacity of from one to two gallons per minute where the oil is heated to a temperature between and F. very satisfactory operation can be attained by using an oil tube approximately three inches in diameter with the plates 21 about one-sixteenth of an inch thick, with a spacing between also approximately one-sixteenth of an inch in size, and with approximately one-thirtysecond of an inch clearance between the perimeter of each plate and the adjacent wall of the tube.

I wish it to be distinctly understood, however, that the several dimensions given above might have to be varied slightly to suit individual conditions, and I do not wish to be limited thereto. The principal point to consider is that the ef fectiveness of heat transfer from or to a viscous liquid seems to bear rather a direct relation to the turbulence of the viscous liquid at the surface where the transfer is taking place. In any event, whatever the theory involved may be, I have found that the eflloiency of a device of this character is greatly increased where the turbulence of the viscous liquid is greatly increased. With my improved device I have found that the rate of heat transfer from or. to the viscous liquid may be raised to a point approximately as high as that of a relatively fluid liquid, such as water.

It will be seen that my improved heater is practically foolproof, that is, no matter of what carelessness the attendant may be guilty, no damage can result. Even should all the water boil away, the heater will not be particularly damaged except possibly for the heating unit 9 which, of course, may burn out in such event. No explosion can take place because of the vent I I, nor is there any fire hazard. ,The oil can not be burned nor overheated and no carbon can form on any of the heating surfaces. My invention, therefore, makes it possible to entirely obviate the necessity of using the various safety devices ordinarily provided for the protection of prior oil heating equipment.

Among other things I have found that the particular turbulence creating means which I employ, namely, the spaced baiiie plates 21 exert a marked cleaning effect upon the oil, small particles of suspended dirt or other foreign matter having a tendency to work themselves down into the spaces between the plates where they accumulate until such time as the unit is removed for In other words, it might be said that my improved apparatus functions as a combined heater and cleaner.

I claim:

A heat exchange device for use with viscous liquids, including a tube through which the viscous liquid is passed, said tube having a multiplicity of spaced baffles lying in planes at an angle to the direction of flow of the viscous liquid, the baffles being arranged to provide flow space for the viscous liquid across their peripheral edges adjacent the tube wall, a core member on which said baffles are mounted, and removable cap means at one end thereof, said core being posi- JAMES M. JENKINS.

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