US3734402A

US3734402A - Vapor generator

Info

Publication number: US3734402A
Application number: US00189949A
Authority: US
Inventors: D Morgan
Original assignee: Thermo Electron Corp
Current assignee: Thermo Fisher Scientific Inc
Priority date: 1971-10-18
Filing date: 1971-10-18
Publication date: 1973-05-22
Anticipated expiration: 1990-05-22
Also published as: IT970712B; DE2247433C3; JPS5114641B2; FR2157543A5; CA955130A; DE2247433B2; DE2247433A1; JPS4848801A

Abstract

A vapor generator for a Rankine cycle engine includes an elongated heat exchange tube for conducting engine working fluid therethrough. A temperature-responsive mechanism extends along the heat exchange tube for sensing the average temperature along its length and also the temperature at any segment of its length. The temperature-responsive mechanism produces a signal from which operation of the vapor generator heat source is influenced as function of either one or both of these temperature conditions.

Description

0 United States Patent 1 1 3,734,402

Morgan [4 1 May 22, 1973 [541 VAPOR GENERATOR 3,511,970 5 1970 Kjellberg ..236/99 x 3,205,871 9/1965 Higgins et a1... ..122/504 [75] Invent Dean Morgan Sudbury Mass 2,565,350 8/1951 Burns et a1. ..236/78 B x [73] Assignee: Thermo Electron Corporation,

Waltham, Mass. Primary ExaminerWilliam E. Wayner [22] Filed: Oct. 18, 1971 Attorney-James L. Neal [21] Appl. No.: 189,949 57 B TRA T A vapor generator for a Rankine cycle engine includes 1.8. CI. B, an elongated heat exchange tube for conducting en- 122/504, 236/99 gine working fluid therethrough. A temperature- [51] Int. Cl. ..F22b 37/47 responsive mechanism extends along the heat [58] Field of Search ..236/2l B, 21 R, 32, exchange tube f sensing the average temperature 236/178 95; 122/504; 73/340 349, along its length and also the temperature at any seg- 368 ment of its length. The temperature-responsive mechanism produces a signal from which operation of [56] References cued the vapor generator heat source is influenced as func- UNITED STATES PATENTS tion of either one or both of these temperature condiions. 2,016,317 10/1935 Dahl ..236/32 2,822,985 2/ 1958 Johnson et a1 ..236/99 11 Claims, 8 Drawing Figures Patented May 22, 1973 3,734AG2 Z5 Sheets-Sheet 1 -12F -2 Patented May 22, 1973 3 Shoots-Sheet 1.1

K164 BURNER CUT-OFF FUEL-AIR CONTROL auauen cur oown 36 242 15g r f f M CONTROL I CONTROL BURNER 5 m Mews BOILER EXPANDER 1 o 'REGEN- 146 Fig 2 ERATOR PUMP couoaussn VAPOR GENERATOR BACKGROUND OF THE INVENTION Rankine cycle engines are experiencing an increase in importance as a result of both technological advances and their relatively pollution-free operation. One area of technological advance involves organic working fluids and vapor generators complimentary to these working fluids. In Rankine cycle systems, efficiency is enhanced by operation at relatively high vapor generator outlet temperatures. Organic working fluids, however, tend to be characterized by maximum temperatures beyond which they will begin to rapidly deteriorate. Some working fluids which are otherwise suitable for use in Rankine cycle systems, when overheated, will not only deteriorate, but will also produce substances which attack certain components of the vapor engine system. Thus, overheating of the working fluid may, in addition to sharply reducing the performance levels of the system, produce permanent damage to the system components.

SUMMARY OF THE INVENTION This invention pertains to a vapor generator for Rankine cycle or vapor engines in which working fluid to be vaporized is circulated through an elongated heat exchange tube. Working fluid in the tube is subject to overheating in at least two ways. First, a relatively large portion of the heat exchange tubing in the vapor generator may become substantially uniformly overheated. Second, overheating may occur along a relatively short segmental portion of the heat exchange tube.

To monitor the temperature of the heat exchange tube, there is provided sensing apparatus which extends therealong lengthwise. The sensing apparatus includes sealed sensing tube means in good thermal communication with the heat exchange tube and containing sensing liquid adapted to vaporize substantially at the maximum temperature to which the working fluid can be heated without deterioration.

Fluid within the sensing tube expands and contracts according to the average temperature change within the heat exchange tube and thus produces a first signal functionally related to such average temperature change. This signal may be used to influence the heat source for the vapor generator to, for example, maintain the system below a preset temperature. Since the sensing fluid within the sensing tube means will vaporize at the maximum temperature which the working fluid can withstand, an abrupt relatively large volumetric expansion of the sensing fluid will be experienced when the maximum temperature is reached in any segmental portion of the heat exchange tube. This abrupt volumetric change of the sensing fluid produces a second signal which indicates a hot spot along some portion of the heat exchange tube. This is usually indicative of some abnormality in the operation of the system. Accordingly, the second signal is appropriately used to override other signals and, for example, cut off the vapor generator heat source.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of one embodiment of this invention;

FIG. 2 is a cross-sectional view of FIG. 1 taken along line 2-2;

FIG. 3 illustrates an alternate embodiment of the invention;

FIG. 4 illustrates another embodiment of the invention;

FIG. 5 is a cut-away view illustrating one embodiment of a control mechanism usable with the apparatus of FIG. 4;

FIGS. 6a and 6b are cross-sectional views of FIG. 5 showing the apparatus in various positions; and

FIG. 7 is a schematic diagram of a Rankine cycle engine incorporating the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Reference will now be made to FIGS. 1 and 2. A vapor engine boiler 10 includes a heat exchange means 12 and a control means 14. A housing 16 for the heat exchange means 12 forms opposed headers. There is shown in FIG. 2 a group of headers designated 18, 20, 22 and 24. Extending between the opposed headers, for conducting working fluid 33 through the heat exchange means 12, are heat exchange tubes which include a set 26 of relatively large tubes 30 and a set 28 of relatively small tubes 32. The tubes 32 have associated therewith a plurality of generally parallel thermally conductive fins 34 situated perpendicularly of the tubes. Spaced from the heat exchange tubes 30 is burner means 36, the intervening space between the burner means and the heat exchange tubes 30 constituting a combustion chamber 37.

Associated with the heat exchange means 12 is the control means 14 including a pair of heat sensing tube means 39 and 41 which include, respectively, relatively

small sensing tubes

38 and 40 extending along the heat exchange tubes 30 and to the housing means 50 for fluid communication with the

bellows

42 and 44. The sensing tube means 39 and 41 are filled with

sensing fluids

56 and 64. Simplicity of operation will, in most circumstances, suggest that sensing

fluids

56 and 64 be identically the same, though this identity is not essential. The

sensing tubes

38 and 40 are mall relative to the heat exchange tubes with which they are associated and may be attached to the associated heat exchange tubes in any convenient manner which produces good thermal conductivity. This conductivity may be accomplished by brazing the

sensing tubes

38 and 40 to the heat exchange tubes 30 and/or 32, with the sensing tubes being either inside or outside of the heat exchange tubes. While the

sensing tubes

38 and 40 are shown as extending along all the heat exchange tubes 30, it should be understood that they may extend along only a portion of those heat exchange tubes or they may be configured to extend along any or all of the relatively small heat exchange tubes 32.

Extending from the bellows 42 is a supporting arm 45 upon which is mounted a microswitch 46 having an actuating member 48. The bellows 42 rests upon the housing means 50. There also extends from the housing means 50 a spring confining member 52 which is bifuricated to extend past the supporting arm 44. Interposed between the member 52 and the bellows 42 is a spring means 54 which applies a predetermined pressure to the sensing fluid 56 in the bellows 42 and the sensing tube 38. Projecting from the bellows 44 is a switch actuating arm 58 which is engageable with the actuator 48 of the microswitch 46. From the housing 50, a second spring confining member 60 extends past the arm 5 8. Between the spring supporting member 60 and the bellows 44 is a spring means 62 which applies a predetermined pressure to the sensing fluid 64 within the bellows 44 and the sensing tube 40. The pressure applied to the sensing fluid 64 in the sensing means 41 is such that the vapor pressure of the sensing fluid 64 will equal the externally applied sensing fluid pressure substantially at the maximum permissable temperature for the working fluid 33 in the heat exchange tubes. In other words, the sensing fluid 64 will vaporize at the maximum permissable working fluid temperature, where the vapor pressure of the sensing fluid equals the externally applied pressure in the sensing fluid. The spring means 54 applies to the sensing fluid 56 in the sensing means 39 sufficient pressure to cause the vapor pressure of the sensing fluid 56 to equal the pressure in the fluid only at a temperature above the maximum permissable temperature for the working fluid 33 and, preferably, only at a temperature above the maximum system temperature which can be anticipated. Consequently, the sensing fluid 56 will vaporize only at a temperature above the maximum permissable temperature for the working fluid 33 and, preferably, will not vaporize at all.

The sensing tube means 39 serves as a thermal expansion monitor for the sensing tube means 41 so that sensitivity of the sensing tube means 41 to the maximum permissable working fluid temperature is not lost. Without the sensing tube means 41, the sensitivity of the sensing tube means 39 to the maximum permissable working fluid temperature would decrease as a function of the length of the sensing tube 40. This occurs because, with relatively long sensing tubes, the thermal expansion and contraction of the sensing fluid attending an overall temperature change within the system will be of such a magnitude that it will become very difficult, if not impossible, to distinguish between sensing fluid volume changes occurring because of such thermal expansion and volume change occurring because of vaporization of sensing fluid at a relatively small segmental length of the sensing tube.

Numerous fluids having a critical temperature above the anticipated maximum system temperature are usable as sensing fluids, the fluid properties being selected as appropriate for each particular system. Examples of suitable sensing fluids are Dowtherm A manufactured by Dow Chemical Company of Midland, Mich; Freon E-3, Freon E-4 and Freon E-5 manufactured of by E. I. du Pont de Nemours & Co., Inc. of Wilmington, Del., and pyridine.

Operation of the apparatus illustrated in FIGS. 1 and 2 will now be described.

The boiler accepts the working fluid 33 through an inlet 66. The working fluid 33 circulates successively through the heat exchange tubes 30 and then through the heat exchange tubes 32 from whence it passes from the boiler through an outlet, not shown. The burner means 36 sustains combustion of a fuel-air mixture in the combustion chamber 37. Products of combustion pass between the

heat exchange tubes

30 and 32 and out through an exhaust passage, not shown, and heats the working fluid in the heat exchange tubes. The temperature of the working fluid must not be permitted to exceed the temperature above which the particular working fluid will begin to deteriorate. Accordingly, the control means 14 provides a signal which may be used to control operations of the burner means 36. One example of such control will be subsequently described in connection with FIG. 7.

The hot products of combustion from the burner means 36 passing through and around the heat exchange tubes 30 heat both the heat exchange tubes and the

sensing tubes

38 and 30. The heat exchange tubes and the sensing tubes have substantially identical temperature profiles. That is, at any location, adjacent segments of tubes will be at the same temperature. When the

sensing fluids

56 and 64 within the sensing tube means 39 and 41, respectively, are heated, they both expand in substantially identical amounts as long as temperatures are below the predetermined maximum temperature for the working fluid 33. As the temperature changes, the volumetric changes of the fluid within the sensing tube means 39 and 41 are equal. An increase or decrease in temperature thereby causes a corresponding movement of both the supporting arm 44 and the switch actuating means 58, as indicated by

arrows

68 and 70, but no relative movement between the microswitch 46 and the actuator arm 58 is produced. The microswitch 46 does not sense the temperature change. However, movement of the supporting arm 44 with its associated microswitch 46 and/or the switch actuating arm 58 may provide a signal as a function of boiler temperature change by actuating the microswitch 59. The actuation of the microswitch 59 may be used to cause a lower stage of combustion in zone 38.

If certain abnormal conditions develop within the boiler 10, hot spots may develop along one or more relatively small linear segments of the heat exchange tube 30. For example, if due to some malfunction of the burner means 36, a large portion of the products of combustion are directed to a relatively small portion of the heat exchange tubes within the boiler, there will develop at this point an excess of heat energy capable of overheating the working fluid 33. In this event, the

sensing fluids

56 and 64 within the

sensing tubes

38 and 40, respectively, will expand by equal volumetric amounts until the predetermined maximum temperature for the working fluid 33 is reached. When this predetermined temperature is reached at any segmental length of the heat exchange tube 30, the sensing fluid 64 in the adjacent segment of the sensing tube 40 will vaporize. The fluid volume within the sensing tube menas 41 will thereby experience a sudden volumetric expansion as compared to the expansion which will take place within the sensing tube means 39. The expansion of the sensing fluid within the sensing tube means 41 will cause the switch actuating arm to move outwardly from the bellows 44, against the bias of the spring 62 and actuate the microswitch 46. The signal from the microswitch 46 may be used to influence the operation of the burner means 36 so as to reduce or en tirely cut off the heat input into the boiler and thereby avoid overheating of the working fluid 33.

A boiler of smaller heat producing capacity is illustrated in FIG. 3 wherein like numerals are used to designate like parts. The apparatus consists of heat exchange means 12 and a control means 14. The heat exchange means includes an insulated tubular wall member forming a chamber within which a heat exchange tube 72 is wound in spiral fashion. Within an interior space formed by the spirally wound heat exchange tube 72 is a burner unit 74 and a baffle structure 76. The burner 74 includes an inlet 76 which admits an air and fuel mixture thereto. The mixture passes through a porous wall 78 of the burner 74 where combustion takes place. The products of combustion pass across a portion of the tube 72, through the baffle 76, onto the remainder of the tube 72 and out through an exhaust opening 80. Working fluid 33 enters the boiler through an inlet 82 of the heat exchange tube 72 and circulates through the tube 72 where it is vaporized. The vapor passes from the tube 72 through an outlet 84 The control means 14 operates in the same manner as when associated with the apparatus described in connection with FIGS. 1 and 2. A pair of sensing tube means 39 and 41 include

sensing tubes

38 and 40, respectively, which extend through the entire length of the heat exchange tube 72, internally thereof. The sensing fluid in the

sensing tubes

38 and 40 is subject to expansion, contraction and vaporization in response to the temperatures existing along the heat exchange tube to provide a signal for influencing boiler operation.

Still another embodiment of the invention is illustrated by FIGS. 4, 5, 6A and 6B. A heat exchange means 85 includes a pair of

headers

86 and 88 which support therebetween a plurality of heat exchange tubes 90. Associated with the heat exchange means 85 is a control means 92. The control means 92 is characterized by sensing tubes 94 which extend singly along the heat exchange tubes 90 rather than in pairs. The control means having a single sensing tube tends to be characterized by tube length limitations not experienced with the dual sensing tube control means. As explained above in reference to FIGS. 1 and 2, if the single tube length is excessively long, the thermal expansion and contraction of sensing fluid in the liquid state will be sufficiently large to create difficulty in distinguishing sensing tube expansion caused by thermal expansion of the sensing fluid from sensing tube expansion caused by vaporization of the sensing fluid at a hot spot along some segment of the heat exchange tube. If the ability to distinguish between these two signals is lost, the ability to detect hot spots is lost. However, for reasons including reasons of economy, it may be advantageous to use the single sensing tube type of control mechanism in some applications.

The control means 92 will be described in connection with the system employing three separate control devices, 93, 95 and 97. It should, of course, be understood that any number of control devices could be used. The control device 93 includes the short sensing tube 94 which extends along the exterior of a pair of heat exchange tubes 90 and through the header 88 to an expansible chamber, or bellows, 100. Extending from the bellows 100 is a plunger 106. Referring to FIGS. 6A and 6B, it will be seen that the plunger 106 is connected to a rocker arm 112 which is biased by a compression spring 114 and pivoted at 116. The rocker arm cooperates with a guide 118 which operates a microswitch 120 to control the burner for the heat exchange means, the burner for the apparatus of FIG. 4 not being shown. A spring 122 is interposed between the bellows 100 and the casing 124 to determine the pressure of the sensing fluid 126 within the control device 93 and thereby the temperature at which the sensing fluid will vaporize, the vaporization temperature being the maximum working fluid temperature. The

control devices

95 and 97 are each contructed in exactly the same fashion as the control device 93. They include, respectively,

short sensing tubes

96 and 98, bellows 102 and 104,

plungers

108 and 110,

rocker arms

128 and 132 having

pivotal connections

130 and 134, and springs 136 and 138 interposed between

bellows

102 and 104 and the casing 124. Each of the

rocker arms

112, 128 and 132 cooperate with the same guide 118 which enables them to operate the single microswitch 120. The

springs

112, 136 and 138 establish identical sensing fluid pressure in each of the

control devices

93, 95 and 97.

When the apparatus of FIGS. 4 through 6 is in operation, working fluid passes from the header 86 through the heat exchange tubes where it is vaporized and then into the header 88. From the header 88, the working fluid vapor passes to other components of the system as will hereafter be described. The products of combustion or other medium from which heat is to be transferred to the working fluid passes around the heat exchange tubes 90, through the spaces between them. The sensing fluid within the

sensing tubes

94, 96 and 98 is responsive to the overall average temperature of the heat exchange tubes with which they are associated. Expansion of the sensing fluids within the

various control devices

93, and 97 will all be relatively small and substantially equal when there is substantially uniform temperature within the heat exchange means 85. The system is constructed so that there is not enough potential thermal expansion of the sensing fluid to cause sufficient movement of the rocker arms and to actuate the microswitch 120. The small movement of the guide 118 which does take place is accomodated by the space 140 which permits the guide to move up and down a little without actuating the microswitch. However, if at least one linear segment of the heat exchange tube 90 reaches the predetermined maximum temperature for the working fluid within the heat exchange tubes 90, this relatively high temperature will cause vaporization of the sensing fluid within the adjacent segment of one of the sensing tubes. The vaporization of the sensing fluid in even a small segment of a sensing tube will produce enough expansion in the fluid volume to operate the microswitch. For example, if a hot spot develops along a heat exchange tube associated with sensing tube 94, the sensing fluid within the sensing tube 94 adjacent the hot spot will evaporate and significantly increase the volume of the sensing fluid within the sensing device 93. The bellows will expand and advance the plunger 106. The plunger 106 will cause the rocker arm 112 to pivot about the support 116 and depress the guide 118 by a sufficient amount to close.

the space 140 and operate the microswitch 120. The microswitch then sends a signal to the system for influencing the operation of the burner, not shown, associated with the heat exchange means 85. Since the rocker arms associated with the various control devices all operate upon a single microswitch, a hot spot occurring adjacent any one of the sensing tubes will causes the microswitch 120 to be actuated. Individual microswitches may be associated with each rocker arm so that the general location of the hot spot can be determined in accordance with which the microswitch is actuated.

FIG. 7 illustrates schematically a Rankine cycle system incorporating this invention. The system includes the burner 36, boiler 12, and control means 14. The working fluid which is evaporated in the boiler 12 and passes to an expander 142 in which it expands to drive the shaft 144. From the expander 142, the vaporized working fluid passes through a regenerator 146 where some of the remaining heat energy is extracted therefrom. The vapor then passes through a condenser 148, is there liquified, and a pump 1S0 drives the liquified working fluid from the condenser 148 back through the regenerator 146. The liquified working fluid is heated in the regenerator and then drive from the regenerator back to the boiler 12 where it is vaporized and the cycle is repeated.

Referring to FIG. 2 with FIG. 7, when the system is operating, the control means 14 monitors the temperature of the boiler as described above. Signals from the control means 14 are fed to the control logic 152. The

control logic then produces a signal for either the burner cut-off means 166 or the burner cut-down means 162.

When there is local overheating at even one small segment of the heat exchange tube in the boiler 12, the signal produced from the microswitch 46 is directed through the control logic 152 to the burner cut-off means 166. The cut-off means 166 commands the fuelair control means 164 to completely terminate the fuel and air supply to the burner 36. In this manner, the system is shut down quickly so that permanent damage is avoided.

In embodiments which employ means responsive to the thermal expansion and contraction of the sensing fluid in its liquid state, the control logic 152 provides a signal for operation of the burner cut-down. means 162. The signal produced by the microswitch 59 is ultimately fed to the burner cut-down means 162 which reduces the fuel-air volume fed to the burner 36 and thereby reduces the overall temperature of the boiler 12. This may serve the usual function of a governor or it may sharply reduce the power output of the system while continuing to provide enough power for low level operation.

The present invention has been described with reference to various preferred embodiments. It should be understood, however, that modifications may be made by those skilled in the art without departing from the scope of this invention.

I claim:

1. A vapor engine boiler comprising:

a. elongated heat exchange tube means for conducting a working fluid along a path in thermal communication with a heat source means;

b. first means extending along said heat exchange tube means and responsive both to the average temperature change in said heat exchange tube means below a predetermined temperature and to the attainment of said predetermined temperature in any segment of said heat exchange tube means;

c. second means extending along said heat exchange tube means and responsive to the average temperature change in said heat exchange tube means; and

d. means responsive to said first and second means for producing a signal capable of influencing boiler operation when said predetermined temperature is attained at any segment of said heat exchange tube means.

2. A vapor engine boiler according to claim 1 wherein said first and second means each comprise a sealed sensing tube means filled with sensing fluid means, sensing fluid means in said first means vaporizing at said predetermined temperature and sensing fluid means in said second means vaporizing at a substantially higher temperature than said predetermined temperature.

3. A vapor engine boiler according to claim 2 further comprising means responsive to said first and second means for respectively producing one signal in response to the attainment of said predetermined temperature in any segment of said heat exchange tube means and another signal proportional to the average temperature change in said heat exchange tube means.

4. A vapor engine boiler comprising:

a. heat source means;

b. elongated heat exchange tube means for conducting working fluid along a path in thermal communication with said heat source means;

c. sealed sensing tube means extending along substantially the entire lenght of said heat exchange tube means in thermal communication therewith, said sensing tube means having a total crosssectional area which is small relative to the crosssectional area of said heat exchange tube means;

d. sensing fluid means filling said sensing tube means,

said sensing fluid means vaporizing at a temperature corresponding to a predetermined maximum temperature for said working fluid, whereby, as the temperature of said working fluid reaches said predetermined maximum along any segment thereof, sensing fluid means within the adjacent segment of said sensing tube vaporizes to cause abrupt volumetric expansion of said sensing fluid means; and

e. means responsive to abrupt expansion of said sensing fluid means for influencing the operation of said heat source means in response to the occurance of said predetermined maximum temperature at any segmental portion of said heat exchange tube means.

5. A vapor engine boiler according to claim 4 wherein said sensing fluid means extends along and engages said heat exchange tube means.

6. A vapor engine boiler according to claim 5 wherein said sensing tube means include expansion chamber means and said responsive means responds to expansion and contraction of said expansible chamber means.

7. A vapor engine boiler comprising:

a. heat source means;

c. a pair of hermetically sealed sensing tubes extending along said heat exchange tube means in thermal communication therewith, said sealed tubes having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means;

d. sensing fluid means filling both said sealed tubes, said sensing fluid means being thermally expansible as a function of working fluid temperature;

e. first expansion chamber means communicating with a first of said sealed tubes;

f. first means biasing said first expansible chamber means to a compressed condition for applying to the sensing fluid means therein a first pressure level, said biasing means causing said sensing fluid means in said first sealed tube to vaporize at a temperature corresponding to a maximum temperature for said working fluid whereby, as the temperature of said working fluid reaches said maximum temperature along any segment of its length, said sensing fluid means within the adjacent segmental length of said first sensing tube vaporizes to cause volumetric expansion of said first expansion chamber means for influencing operation of said heat source means in response to temperature conditions at relatively short segments of said heat exchange tube means;

g. second expansible chamber means communicating with a second of said sealed tubes; and

h. second means biasing said second expansible chamber means to a compressed condition for applying to the sensing fluid therein a second pressure level, said second pressure level being sufficiently high to cause said sensing fluid means in said second sealed tube to vaporize at a temperature above said maximum temperature for said working fluid, whereby two signals are produced, a first of said signals being proportional to temperature change below said maximum temperature and also responsive to the attainment of said maximum temperature along any segment of said heat exchange tube, the second of said signals being proportional to temperature change both below and above said maximum temperature and independent of said maximum temperature; and

i. means responsive to said first and second signals for influencing the operation of said heat source means as a function of the occurance of said maximumtemperature along any segment of said first sealed tube.

8. A vapor engine boiler according to claim 7 wherein said responsive means responds to both said first signal and said second signal for influencing said heat source means as a function of the occurrence of said maximum temperature along any segment of said heat exchange tube means.

9. A vapor engine boiler comprising:

a. heat source means;

c. sealed sensing tube means extending along said heat exchange tube means in thermal communication therewith, said sensing tube means having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means;

(1. sensing fluid means filling said sensing tube means, said sensing fluid means being thermally expansible as a function of working fluid temperature;

e. means for applying pressure to said sensing fluid means in said sensing tube means for establishing a predetermined vaporization temperature of said sensing fluid means whereby, as the temperature of said working fluid within any segment of said heat exchange tube means reaches a temperature level substantially equalling such predetermined vaporization temperature, said sensing fluid means within the adjacent segmental length of said sensing tube means vaporizes; and

f. means responsive to vaporization of said sensing fluid means for influencing the operation of said heat source means. 10. A vapor engine boiler according to claim 9 wherein said responsive means is also responsive to thermal expansion and contraction of said sensing fluid means for influencing said heat source in response thereto.

11. A vapor engine boiler comprising:

a. heat source means; b. thermally sensitive working fluid for said vapor engine;

c. elongated heat exchange tube means for conducting said working fluid along a path in thermal communication with said heat source means;

(1. sealed sensing tube means extending along a substantial length of said heat exchange tube means in thermal communication therewith, said sensing tube means having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means;

e. sensing fluid means filling said sensing tube means,

said sensing fluid means being thermally expansible as a function of working fluid temperature;

f. means for maintaining the pressure internal of said g. means responsive to the expansion of said sensing fluid means attending such vaporization thereof for reducing the heat output of said heat source means.

Claims

1. A vapor engine boiler comprising: a. elongated heat exchange tube means for conducting a working fluid along a path in thermal communication with a heat source means; b. first means extending along said heat exchange tube means and responsive both to the average temperature change in said heat exchange tube means below a predetermined temperature and to the attainment of Said predetermined temperature in any segment of said heat exchange tube means; c. second means extending along said heat exchange tube means and responsive to the average temperature change in said heat exchange tube means; and d. means responsive to said first and second means for producing a signal capable of influencing boiler operation when said predetermined temperature is attained at any segment of said heat exchange tube means.

4. A vapor engine boiler comprising: a. heat source means; b. elongated heat exchange tube means for conducting working fluid along a path in thermal communication with said heat source means; c. sealed sensing tube means extending along substantially the entire lenght of said heat exchange tube means in thermal communication therewith, said sensing tube means having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means; d. sensing fluid means filling said sensing tube means, said sensing fluid means vaporizing at a temperature corresponding to a predetermined maximum temperature for said working fluid, whereby, as the temperature of said working fluid reaches said predetermined maximum along any segment thereof, sensing fluid means within the adjacent segment of said sensing tube vaporizes to cause abrupt volumetric expansion of said sensing fluid means; and e. means responsive to abrupt expansion of said sensing fluid means for influencing the operation of said heat source means in response to the occurance of said predetermined maximum temperature at any segmental portion of said heat exchange tube means.

7. A vapor engine boiler comprising: a. heat source means; b. elongated heat exchange tube means for conducting working fluid along a path in thermal communication with said heat source means; c. a pair of hermetically sealed sensing tubes extending along said heat exchange tube means in thermal communication therewith, said sealed tubes having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means; d. sensing fluid means filling both said sealed tubes, said sensing fluid means being thermally expansible as a function of working fluid temperature; e. first expansion chamber means communicating with a first of said sealed tubes; f. first means biasing said first expansible chamber means to a compressed condition for applying to the sensing fluid means therein a first pressure level, said biasing means causing said sensing fluid means in said first sealed tube to vaporize at a temperature corresponding to a maximum temperature for said working fluid whereby, as the temperature of said working fluid reaches said maximum temperature along any segment of its length, said sensing fluid means within the adjacent segmental length of said first sensing tube vaporizes to cause volumetric expansion oF said first expansion chamber means for influencing operation of said heat source means in response to temperature conditions at relatively short segments of said heat exchange tube means; g. second expansible chamber means communicating with a second of said sealed tubes; and h. second means biasing said second expansible chamber means to a compressed condition for applying to the sensing fluid therein a second pressure level, said second pressure level being sufficiently high to cause said sensing fluid means in said second sealed tube to vaporize at a temperature above said maximum temperature for said working fluid, whereby two signals are produced, a first of said signals being proportional to temperature change below said maximum temperature and also responsive to the attainment of said maximum temperature along any segment of said heat exchange tube, the second of said signals being proportional to temperature change both below and above said maximum temperature and independent of said maximum temperature; and i. means responsive to said first and second signals for influencing the operation of said heat source means as a function of the occurance of said maximum temperature along any segment of said first sealed tube.

9. A vapor engine boiler comprising: a. heat source means; b. elongated heat exchange tube means for conducting working fluid along a path in thermal communication with said heat source means; c. sealed sensing tube means extending along said heat exchange tube means in thermal communication therewith, said sensing tube means having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means; d. sensing fluid means filling said sensing tube means, said sensing fluid means being thermally expansible as a function of working fluid temperature; e. means for applying pressure to said sensing fluid means in said sensing tube means for establishing a predetermined vaporization temperature of said sensing fluid means whereby, as the temperature of said working fluid within any segment of said heat exchange tube means reaches a temperature level substantially equalling such predetermined vaporization temperature, said sensing fluid means within the adjacent segmental length of said sensing tube means vaporizes; and f. means responsive to vaporization of said sensing fluid means for influencing the operation of said heat source means.

10. A vapor engine boiler according to claim 9 wherein said responsive means is also responsive to thermal expansion and contraction of said sensing fluid means for influencing said heat source in response thereto.

11. A vapor engine boiler comprising: a. heat source means; b. thermally sensitive working fluid for said vapor engine; c. elongated heat exchange tube means for conducting said working fluid along a path in thermal communication with said heat source means; d. sealed sensing tube means extending along a substantial length of said heat exchange tube means in thermal communication therewith, said sensing tube means having a total cross-sectional area which is small relative to the cross-sectional area of said heat exchange tube means; e. sensing fluid means filling said sensing tube means, said sensing fluid means being thermally expansible as a function of working fluid temperature; f. means for maintaining the pressure internal of said sensing tube means at a value which will result in vaporization of said sensing fluid means at a predetermined temperature substantially equalling the maximum temperature to which said working fluid can be heated without deterioration, whereby as the temperature of said working fluid within any segment of said heat exchange tube means reaches said predetermined temperature said sensing fluid means within the adjacent segment of said sensing tube means vaporizes; and g. means responsive to the expansion of said sensing fluid means attending such vaporization thereof for reducing the heat output of said heat source means.