[Fig. 936.] represents the external appearance of the refrigerator, enclosed in a cylindrical case; [fig. 937.], the same, one-half of the case being removed to show the form of the apparatus within; and [fig. 938.], a section cut through the middle of the apparatus perpendicularly, for the purpose of displaying the internal figure of the spiral channels.
The apparatus is proposed to be made of sheet copper, tinned on its surface, and is formed by cutting circular pieces of thin copper, or segments of circles, and connecting them together by rivets, solder, or by any other convenient means, as coppersmiths usually do; these circular pieces of copper being united to one another, in the way of a spiral or screw, form the chambers through which the fluids are to pass within, in an ascending or descending inclined plane.
In [figs. 937.] and [938.], a, a, is the central tube or standard (of any diameter that may be found convenient), round which the spiral chambers are to be formed; b, b, are the sides of the outer case, to which the edges of the spiral fit closely, but need not be attached; c, c, are two of the circular plates of copper, connected together by rivets at the edges, in the manner shown, or by any other suitable means; d, is the chamber, formed by the two sheets of copper, and which is carried round from top to bottom in a spiral or circular inclined plane, by a succession of circular plates connected to each other.
The hot fluid is admitted into the spiral chamber d, through a trumpet or wide-mouthed tube e, at top, and is discharged at bottom by an aperture and cock f. The cold water which is to be employed as the cooling material, is to be introduced through the pipe g, in the centre, from whence discharging itself by a hole at bottom, the cold water occupies the interior of the cylindrical case b, and rises in the spiral passage h, between the coils of the chamber, until it ascends to the top of the vessel, and then it flows away by a spout i, seen in [fig. 936.]
It will be perceived that the hot fluid enters the apparatus at top, and the cold fluid at bottom, passing each other, by means of which an interchange of temperatures takes place through the plates of copper, the cooling fluid passing off at top in a heated state, by means of the caloric which it has abstracted from the hot fluid; and the hot fluid passing off through the pipe and cock at bottom, in a very reduced state of temperature, by reason of the caloric which it held having been given out to the cooling fluid.
