WO2015059537A2

WO2015059537A2 - Improved type of heat exchanger preferably applicable to gaseous fuel ovens

Info

Publication number: WO2015059537A2
Application number: PCT/IB2014/002084
Authority: WO
Original assignee: Tecnoinox S.R.L.
Priority date: 2013-10-11
Filing date: 2014-10-11
Publication date: 2015-04-30
Also published as: ITPN20130061A1; EP3055622A2; EP3055622B1; WO2015059537A3

Abstract

Improved type of heat exchanger preferably applicable to gaseous fuel ovens. The mentioned improved type of (SC) heat exchangers are placed into the cell of an oven (F), precisely on its bottom, (SC) and fitted vertically on top of the burners (BR). The above mentioned (SC) heat exchangers are characterized by the fact that there are several pipe elements (T) and that on such pipe elements, beads (B) are created towards the inner part of the (T) pipe elements; Heat exchanger (SC), as in the previous claim, are characterized by the fact that the (B) beads are practiced on the (T) pipe elements of the (SC) heat exchanger, (B) are preferably placed one opposite to the other, in order to generate a reduction of the section area inside the (T) pipe element so as to create a sort of "Venturi" nozzle; Heat exchanger (SC), as in the previous claim, are characterized by the fact that the (B) beads pressed on the (T) pipe element, as well as being opposed one to each other, result to be (B) practiced on above mentioned (T) pipe element with an alternating pattern with a preferred angle of 90 degrees.

Description

Patent application for industrial invention under the title:

"IMPROVED TYPE OF HEAT EXCHANGER PREFERABLY APPLICABLE TO GASEOUS FUEL OVENS

Requestor: TECNOINOX S.r.l.

Nationality Italian

Address: 33080 PORCIA (PN) - Via Torricelli, 1

DOM. N° DEL:

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The object of the present invention is the application of a particular kind of heat exchanger to improve the efficiency of the heat exchange in gaseous fuel ovens. Such heat exchangers are composed of pipe elements, of suitable length, that start from the gas burner area and extend vertically like "organ pipes" and they present a bead structure carefully studied in order to increase the surface area for heat exchange and alternate sections of the pipes where the hot gases flow slowly and fast. This shape generates some minor pressure losses so that the total time spent by the hot gases in the heat exchangers increases without compromising their regular outflow from the duct and the quality of the combustion. Overall, with such heat exchangers, the heat exchanged with the baking chamber will be more uniform and a smaller amount of energy will flow through the oven outlet duct and be wasted.

The most common and well-known heat exchangers use different shapes to spread in the best possible way the heat from the hot gases flowing from the burners. They usually fail to achieve an optimal distribution because of several reasons (shape miscalculated, use wrong materials or the flow is not uniformly hot) therefore it is necessary to use fans to convoy the air from the heat exchanger area to the rest of the oven chamber. As in some cases, the fans in the ovens, over the primary function of evening the temperature in the baking chamber, have also the secondary purpose of cooling and warming the heat exchangers themselves when the heat in the gases within has brisk variations. Thus, the fans also help the heat exchangers to reach a thermal equilibrium. We will not discuss any further the state of art of heat exchangers as experts in the sectors and people who studied heat transfer theory already know well this topic.

The purpose of the presented invention is to offer an improved alternative to solve the drawbacks and limitations found on heat exchangers for gas ovens currently in use and on sale.

In the following list, which may not be exhaustive and is to be used for examples, you can find the explanations of the attached figures in order to better understand the details and the advantages of the heat exchangers presented in this invention:

o Figure 1 shows a common gas oven in a three-quarter view

o Figure 2 shows the same oven as Figure 1 sketched lightly with the heat exchangers and the burners positioned underneath highlighted by a bolder line o Figure 3 shows only the ensemble heat exchangers - burners as highlighted in Figure 2

o Figure 4 is a section view of a heat exchanger where the predicted flow of the hot-burnt gases inside it is sketched.

It is useful to underline that the same denomination will be used for the same details throughout the following explanation and in the previous figures. The oven depicted in figure 1 is a standard gas oven F equipped with an outlet vent C, sometimes called chimney, for the outlet of hot-burnt gases already employed to provide heat to the oven F chamber. Such oven is also equipped with devices to force air circulation in the chamber such as one or more fans V placed in the back of the chamber and next to the heat exchangers SC.

Figure 2 shows that in the bottom are of the mentioned oven F are positioned one or more burner elements B on top of which several pipe elements T are placed; this follows the standard layout and is nothing new. The new concept is the shape of these pipe elements T that present beads B on their longitudinal development which improve the efficiency of the heat exchange when comparing the presented heat exchangers SC to the current state of art.

There are at least 2 reasons why such pipe elements T with the beads B on their surface make for improved heat exchangers SC:

o The first reason is that the beads B cause an increase of the surface area of the heat exchanger SC, precisely between the pipe element T and the baking chamber of the oven F. This is a rather straightforward way to increase the heat exchange.

o The second reason, not less important, is that the numerous change in the

section area of the pipe element T, as the beads B cause alternating increases and decreases of the section, generate an oscillatory speed pattern of the hot gases. In fact, due to the so-called Venturi effect, the flow accelerates when the section area becomes smaller and decelerates when the section area grows larger. The beads alternating pattern, because of studies and test trials, presents more expansion areas so that the overall speed of the hot-burnt gases inside the heat exchangers SC is lower than in standard heat exchangers. This has a positive effect because it causes an increase in the heat transferred from the hot- burnt gases to the air in the chamber. Anyway, such reduced speed does not create any obstacle or disadvantage in the flow towards the hot gases outlet vent C. It is useful to underline that the pattern of the beads B causing enlargements and reductions in the section area of the pipe elements T was properly studied, the size of the beads B carefully sized and the distance between them was chosen so that there are no vortex areas where the hot-burnt gases would basically stop flowing towards the outlet vent C. The hot-burnt gases can flow regularly towards the outlet vent C in standard atmospherical conditions or with the help of an aspirator.

In figure 4 the flow of the hot gases is depicted with short and wide arrows for areas where the speed decreases and with long and thin arrows for areas where the speed increases.

It is understood that several variations to the presented invention may arise without exceeding the limits of the concept described here above and claimed as industrial intellectual private property.

Claims

1) Improved type of heat exchanger preferably applicable to gaseous fuel ovens.

The mentioned improved type of (SC) heat exchangers are placed into the cell of an oven (F), precisely on its bottom, (SC) and fitted vertically on top of the burners (BR). The above mentioned (SC) heat exchangers are characterized by the fact that there are several pipe elements (T) and that on such pipe elements, beads (B) are created towards the inner part of the (T) pipe elements;

2) Heat exchanger (SC), as in the previous claim, are characterized by the fact that the (B) beads are practiced on the (T) pipe elements of the (SC) heat exchanger, (B) are preferably placed one opposite to the other, in order to generate a reduction of the section area inside the (T) pipe element so as to create a sort of "Venturi" nozzle;

3) Heat exchanger (SC), as in the previous claim, are characterized by the fact that the (B) beads pressed on the (T) pipe element, as well as being opposed one to each other, result to be (B) practiced on above mentioned (T) pipe element with an alternating pattern with a preferred angle of 90 degrees.