Heat recovery device for a fireplace - Patent Review GB19840026487 19841019

Description

SPECIFICATION

Heat recovery device for a fireplace

This invention relates to a heat recovery device for a fireplace.

Considering the recent great increase in the cost of fuels, all heating elements must be made to achieve maximum absorption of the heating capacity which may be obtained from fuel in order to reach a high thermal efficiency.

As is well known, traditional fireplaces have a serious drawback in that they waste a large amount of the heat obtained from fuel combustion. Such fireplaces are gradually being relegated to purely decorative functions since their use entails a large number of inconveniences inasmuch as the rest of the rooms of the premises concerned require the use of various other types of heating as well as the fact that, as already mentioned, these traditional fireplaces waste a great amount of heat, at a consequently very high cost.

It is an object of the present invention to provide a heat recovery device for a fireplace which operates with maximum safety and efficiency.

With this object in view, the invention provides a heat recovery device for a fireplace comprising a generally horizontally arranged grate having bars which consist of interconnected hollow tubes, an upright hollow panel which is connected to the rear edge of the grate, has a front surface facing the grate of saw-toothed profile, and has an upper sloping part projecting across the grate towards the mouth of the fireplace in which the device is to be installed, and a horizontally arranged tank which is located directly above the grate and has a cross-section substantially in the form of an inverted triangle, the two lower sides of which are saw-toothed in profile.

Given its characteristics and design, the proposed recovery device may be very easily installed in existing fireplaces, especially in those with a very high mouth. To this end, the heat recovery device of the invention includes a hollow grate which is preferably composed of a number of tubes arranged side by side, at equal distances from each other, perpendicular to the mouth of the fireplace and set on the same horizontal plane. The aforementioned tubes are preferably firmly attached at their front ends to a horizontal metal bar which is also hollow and is interconnected with the tubes through which water of a heating network (which absorbs the heat) circulates.

The rear ends of the tubes are firmly attached to the main recovery panel, which is likewise hollow and has a front surface which is saw-toothed in cross-section so as to provide a substantial increase in the internal contact surface of the panel through which water circulates. The external surface of the panel, which is heated by upwardly directed flames when there is a fire burning in the grate, is likewise substantially increased while the aforesaid saw-toothed profile causes the flames to adapt themselves to the profile and lie adjacent same for the longest possible time.

At a certain distance above the grate, the main panel has an ascending upper part sloping toward the mouth of the fireplace. This sloping part is of great importance in achieving optimum utilization of the heat produced by combustion since the current of heat thus produced ascends and therefore impinges substantially perpendicularly on the sloping part of the panel.

The distance between the grate and the sloping part of the main panel is critical to the efficiency of heat recovery of the device. A relatively large distance, as would be necessary to preserve the good appearance of a fireplace with a mouth of great height, would lead to a substantial reduction in the thermal efficiency of combustion due to the loss of a large quantity of calories over that distance. In other words, these calories could not be absorbed by the sloping front surface of the upper part of the main recovery panel as a result of its excessive height above the grate.

It is to obviate the need for such a large distance between the grate and the sloping part that the horizontally-arranged tank is installed at a certain distance, horizontally, from the upper end of the main panel. The external faces of the tank, except the top face, also present surfaces having saw-toothed profile similar to the aforementioned front surface of the main panel.

The horizontal axis of the tank is preferably positioned in a substantially vertical plane directly above the middle of the grate and parallel to the mouth of the fireplace so that when there is a fire in the grate the flames and heat flow which rise vertically and perpendicular to the grate also impinge directly upon the external saw-toothed sides of the tank. Water in the tank is thus heated and absorbs a large quantity of the heat produced in combustion. The efficiency of thermal utilization of the device is further enhanced since heat which is not absorbed by the panel is channelled to impinge on the rear external face of the horizontal tank.Furthermore, heat which is not absorbed by the tank is advantageously channelled along the rear face of the tank so that it in turn may impinge on a second panel of characteristics similar to those of the main panel but installed higher up the rear of the fireplace.

The tank and the second panel are preferably interconnected and, in turn, they may be connected to the main panel. A duct may be provided in the uppermost region of the second panel for connection with a heating net work of a building.

It should be borne in mind that the horizontal tank, due to its location, performs a twofold function. Firstly, as has been previously mentioned, the position of the horizontal tank directly above the middle of the grate allows it to absorb a large quantity of heat. At the same time, thanks to the position of the tank, the top of the main panel and the lower edge of the second panel cannot be seen from outside the fireplace. This latter function is important since sight of the panel edges would be undesirable from the standpoint of the appearance of the fireplace considering that household fireplaces also have a highly appreciated decorative value.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a vertical cross-section illustrating a preferred embodiment of the heat recovery device of the invention installed in a conventional fireplace; and

Figure 2 is a vertical cross-section in a plane perpendicular to Fig. 1 illustrating the same heat recovery device as seen from the front.

Fig. 1 shows that a preferred embodiment of the heat recovery device of the invention is basically composed of a grate 10 formed by a number of tubes set at equal distances from each other so that their front ends are firmly connected to a hollow metal bar 11 while their rear ends are connected to a main panel1 2. The main panel1 2 is hollow and has a front surface of saw-tooth profile. It comprises a lower vertical part and an under part1 3 sloping toward the mouth of the fireplace where the device is installed.

Thanks to the aforementioned saw-tooth profile of the panel front surface, a greater area of heat exposure is achieved while the flames produced in combustion are retained and remain in contact with the main panel1 2 for a longer time. A greater quantity of heat is thus absorbed by water circulating through the main panel1 2 than would be the case with a flat surfaced panel.

At a certain distance from the sloping part

1 3 of the main panel 12, a horizontally arranged tank 14 is installed in the fireplace.

The cross-section of the tank 14 is in the form of an inverted triangle and the two lower sides have a saw-toothed profile. The aforesaid tank

14 is positioned directly above the middle of the grate 10 parallel to the mouth of the fireplace in which the grate 10 is located. As has been previously mentioned, this is of great importance because the heat produced in combustion ascends vertically and perpendicularly from the grate 10 thus impinging directly on the tank 14 which absorbs a substantial amount of heat from this ascending flow.

It should be noted that thanks to the sloping part1 3 of the main panel 12, the heat which has not been absorbed by the main panel1 2 is channelled so as to impinge substantially perpendicularly on the rear face1 5 of the tank 14. This brings about an increase in heat absorption from the ascending flow and prevents the waste of heat, which would otherwise be lost by discharge through the chimney.The surplus heat which can not be absorbed by the tank 14 is further channelled, thanks to the slope of the rear tank face 15, onto a second panel1 6, whose characteristics are quite similar to those of the sloping part1 3 of the main panel1 2. The second panel1 6 is arranged above the sloping part1 3 of the main panel1 2 and generally parallel thereto and it also has a front surface of saw-toothed profile to improve heat absorption.

Thanks to its position the tank 14 prevents the upper end of the panel1 3 and the beginning or lower edge of the second panel1 6 from being seen from the mouth1 8 of the fireplace. This tank 14 is of great importance for achievement of good heat utilisation because the heat recovery device is specially designed to be installed in fireplaces with a large mouth and substantial height where, if the device were not suitably positioned and the aforementioned tank 14 did not exist, the heating efficiency of the assembly would be quite low.Also, if the tank 14 was not present the upper end of the main panel1 3 and the lower edge of the second panel1 6 would be visible from the mouth of the fireplace which would be undesirable from the standpoint of its appearance when one bears in mind the great importance attached to the decorative function of fireplaces.

The main panel 12, the tank 14 and the second panel1 6 are interconnected by a number of tubes and a tube is installed in the uppermost part of the second panel1 6 to allow connection of the assembly to a heating network which may be composed of several radiators installed in different areas or rooms of the home in which the heat recovery device is installed. Return of water from the conventional heating network is provided for through the metal bar 11.

It will be appreciated that the heat recovery device of the invention is a simple and effective construction. Of course, the invention is not limited to the exact details of the illustrated embodiment which is given merely by way of example. Many variations are possible within the scope of the claims.