The Economiser

Source : The Engineer, Dec. 14, 1917, p. 516 - Part 1 - The Economiser
Date of patent : 1816
Patent #: 4081

All my improvements for diminishing the consumption of fuel consist of the different forms or modifications of a new method, contrivance, or mechanical arrangement for heating and cooling liquids, airs or gases, and other bodies by the use of which contrivance heat is a abstracted from one portion of such liquids, airs, and other bodies and communicated to another portion with very little loss; so that in all cases where a constant succession of heated liquids or other bodies is required, the quantity of fuel necessary to maintain or supply it is by this contrivance greatly diminished.

The first modification of said contrivance or arrangement is described as follows:

Stirling's Economiser and Hot Air Engine - Fig. 1

A.B. fig. 1 is a pipe, channel or passage, formed of metal, stone, bricks or other materials according to circumstances i.e. according to the chemical agencies of the bodies to be heated or cooled and the degree of heat in said bodies. The hot liquid, gas, or body to be cooled is by any means made to enter the passage at A and to pass along to its other extremity B.
In its progress it gives out its heat to the sides of the passage or to any bodies contained in it and issues at B at nearly the original temperature of the passage.

In this manner the extremity at A and a considerable portion of the passage is heated to nearly the temperature of the hot liquid while the extremity B still retains its original temperature nearly. When the temperature of the passage at B has been raised a few degrees the motion of the fluid from A to B is stopped and a portion of fluid which is required to be heated and which is supposed to be a few degrees colder than the extremity of the passage at B is made to traverse the same passage in a contrary direction i.e. from B to A; by which means it receives heat from the sides of the passage or other bodies contained in it and issues at A at early the same temperature with the fluid to be cooled. When the temperature of the passage at A has thus been lowered a few degrees, the process is again stopped and a portion of the fluid to be cooled is made to pass from A to B and so on alternately.

Stirling's Economiser and Hot Air Engine - Fig. 2

The second modification of any said contrivance or arrangement consists in interposing a thin plate of metal or other materials, according to circumstances, between two currents of liquid gas or vapour which are made to run in opposite directions.

A.B. fig. 2 represents such a plate and c.d., two passage between which it is interposed. The fluid to be cooled is made to traverse the passage d from A to B and the fluid to be heated is made to tranverse the passage d from B to A.
The extremity of the plate at A is kept hot by the current in d and the extremity B is kept cold by the current in c. The plate A.B. abstracts the heat from the fluid in the passage d and communicates it to that in c with very little loss.The waste or escape of heat from the passage is prevented by their being surrounded with charcoal powder, wood, bricks or any substance that does not easily permit heat to pass through it.

In the construction of the passage in both Modification of my contrivance for heating and cooling liquids and other bodies I observe the following rules:

  1. When the passage are made of metal or any other substance that conducts or transmits heat easily I make the metal or other substance as thin as possible to prevent the heat from being transmitted in this manner from the hot to the cold extremity of the passage.

  2. Liquids and airs being very imperfect conductors of heat I make the passages very narrow (at least in one direction) in proportion to their length, for the purpose of heating and cooling more completely the liquids or airs that pass through them. A transverse section of the passages is given at A, B and C fig. 3.

  3. When the passage cannot be made sufficiently narrow I make their sides jagged or rough by bodies projecting form them as represented at fig 4 or I adopt any similar method for promoting the internal motions of the fluids and the ready communication of heat to them or to the passage.

  4. When the width of the passage cannot be sufficiently diminished increase its length in order to attain the same end. The form and construction of the tubes, passages and plates in both the modifications of my general contrivance or arrangement may be varied according to circumstances; but the benefit to be derived from this contrivance arises from the fluids and other bodies to be heated and those to be cooled being made to move in opposite directions and it is for the invention or improvement of this arrangement that I have applied for and obtained His Majesty’s Letter Patent.

Stirling's Economiser and Hot Air Engine - Fig. 2