FR2469661A1 - Economiser for central heating system - has heat exchanger condensing moisture in flue gases to preheat boiler return - Google Patents

Abstract

The economiser has a steel casing (6) with a corrosion resistant inner surface. It has an entry (7) and outlet (8) for flue gases at high level separated by a vertical partition (9) to compel the gases to follow a U-shaped path. A bundle of U-tubes dips into the casing with one arm of each U on each side of the partition (9). One set of arms is connected into an inlet header (2) and the other set into an outlet header (4). The headers are connected in the boiler water return. Heat is transferred to the water by condensation of the moisture in the flue gases.

Description

 The subject of the present invention is an accessory intended to be easily mounted in existing central heating installations burning a hydrocarbon-based fuel and more specifically gas heating installations which do not present the problems of fouling and maintenance. oil heating.

 This accessory is essentially a heat exchanger recuperator designed to condense all or part of the water vapor contained in the combustion gases coming from the boiler and going to the chimney, by cooling it with 11 "cold" water from the heating circuit returning to the boiler, the latent heat of vaporization of water being taken advantage of during condensation to preheat this "cold" water, thus achieving recovery of this latent heat which would otherwise go to the chimney .

For this purpose, the heat exchanger recuperator is connected, as regards its "hot" part, in the exhaust duct going from the combustion chamber of the boiler to the chimney and, as regards its part "cold", at a point in the return pipe for the water coming from the radiators and ending at the boiler.

 The description which follows with reference to the appended drawings, given by way of nonlimiting example, will make it clear how the invention can be implemented.

 Figure 1 is a sectional view of an embodiment of the apparatus of the present invention.

 FIG. 2 is a general diagram of the mounting of this device in a current central heating installation.

The embodiment illustrated in FIG. 1 is a heat exchanger recuperator R comprising
- on the one hand, pins 1 or bundle of 56 stainless steel tubes 1.6 mm thick and 21.3 indri in diameter, connecting at one end to a water inlet manifold 2 of which the connector is shown at 3 and at the other end to a water outlet manifold 4 whose connector is shown at 5, the two collectors 2 and 4 being arranged side by side at the top of the device;
- on the other hand, a casing 6 in black ttle treated with the application of a physically and chemically neutral material, resistant to corrosion, this casing 6 having upwards a lateral smoke inlet orifice 7 and an opposite lateral orifice smoke outlet 8, with a baffle 9 interposed between them on the smoke path, a condensate discharge being provided at 10 at the bottom of the casing.

 FIG. 2 shows a standard installation for central heating of residential premises. There is a boiler II of which we see at 12 the arrival of combustible gas and at 13 the flue or smoke evacuation duct, possibly equipped with an extractor 14 and leading to the chimney 15. The fluid circuit coolant, in this case water, contains radiators such as 16 and there is shown at 17 the starting section of the boiler II and at 18 the loop back to it. A bypass 19 with three-way valve 20 and a recycling pump 21 are provided as usual, as is a booster pump 22.

The mounting of the recuperator R of the present invention is done, after cutting off the flue 13, by connecting the latter to the smoke inlet 7 and smoke outlet 8 ports respectively. For their part, the water inlet 3 and water outlet 5 connections are connected respectively, by connection pipes 23 and 24, at two points 25 and 26 of the return loop 18, a valve 27 being disposed between these two points to impose on an adjustable fraction of the flow of "cold" water leaving the radiators 16, the route by the recuperator R via the connection pipes 23 and 24.

 The length of the pins is calculated according to the expected exchange rate, taking into account the respective temperatures of the fluids present.

The device R must allow energy recovery in the case where the heating installation consists of radiators. In this case, the temperature of the heat transfer fluid, thanks to which the recovered energy is reintroduced into the network varies from 200 to 70GCo
In the case of an installation whose heating bodies consist of submerged tubes (underfloor heating), the temperature of the heat transfer fluid varies from 150 to 400C.

 In both cases, the temperature of the fumes entering 7 into the recuperator R is of the order of 250 C and, after exchange, and depending on the type of installation, it will vary between 350 and 800C.

 As a reminder, the condensation of the water contained in the fumes occurs when the "recovery" fluid is at a temperature of the order of 580C or below.

 Recovery is then maximum since the latent heat of vaporization benefits the network.

Claims (2)

 1. A thermal energy saving device intended to be incorporated into a heating installation, characterized in that this device is a heat exchanger recuperator designed to condense all or part of the water vapor contained in the combustion gases from the boiler and going to the chimney, by cooling these with "cold" water from the heating circuit returning to the boiler, the latent heat of vaporization of water being taken advantage of during its condensation to preheat this water "cold", thus achieving recovery of this latent heat. 2. Apparatus according to claim 1, characterized in that it is connected, as regards its "hot" part, in the exhaust duct going from the combustion chamber of the boiler to the chimney and, for this which is in its "cold" part, at a point in the batten return pipe coming from the radiators and ending at the boiler.