JPH0147703B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the construction of a heat exchanger for an electric instantaneous water heater using a sheathed heater.

Construction of a conventional example and its problems A conventional heat exchanger for an electric instantaneous water heater of this kind is constructed as shown in FIG. is installed inside the sheathed heater 1, and both ends of the sheathed heater 1 are connected to the crown plate 3.
is watertightly brazed. A water inlet pipe 4 is brazed to the lower surface of the can body 2, and a hot water outlet pipe 5 is inserted close to the crown plate 3 and brazed to the can body 2.

In this electric instantaneous water heater equipped with a heat exchanger, when the pot is opened and water is supplied, the sheathed heater 1 is energized, and the water flowing in from the water inlet pipe 4 enters the can body 2. It rises while being diffused, reaches near the crown plate 3 while being heated by the sheathed heater 1, and is then discharged through the outlet pipe 5.

By the way, the heat exchanger of an electric instant water heater has a heating capacity commensurate with the hot water temperature and flow rate.
The sheathed heater 1 requires a high thermal output density. In addition, heat exchange performance is required to ensure that the temperature of the hot water rises quickly after the start of hot water dispensing, and that there is little after-boiling after the water stops.

However, in the structure described above, the speed at which the water flowing into the can body 2 rises and contacts the pipe wall of the sheathed heater 1 is uneven depending on the position.
The velocity of flow between the coil layers is extremely low. Therefore, heat transfer is not uniform. Further, water far from the pipe wall of the sheathed heater 1 bypasses and flows mixedly into the hot water tap pipe 5. As a result, the temperature of the hot water rises slowly after the start of hot water dispensing, and in terms of heat exchange performance, it exhibits characteristics that are a combination of an instantaneous type and a storage type. In addition, the temperature of the tube wall of the sheathed heater 1 in areas where heat transfer is poor increases excessively, and this heat accumulation increases after-boiling after water stops, and repeated use can cause dielectric breakdown in areas where the temperature rises. There's a problem.

Purpose of the Invention The present invention solves the above-mentioned conventional drawbacks, and has a configuration in which the flow velocity of water in contact with the pipe wall of a sheathed heater is increased, and the flowing water is also passed between the coil layers of the sheathed heater, so that the rise is quick and the after-boiling is prevented. The objective is to obtain a heat exchanger that is small in size and has excellent durability.

Structure of the Invention In order to achieve the above-mentioned object, the present invention forms a sheathed heater that is coil-shaped and has a coil diameter that gradually decreases toward the lower end. The heat exchanger is configured to improve uneven heat transfer by passing between the layers of the sheathed heater coil and raising the inside of the coil by the centripetal flow generated as the heat is raised.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In the figure, 6 is a sheathed heater shaped like a so-called bamboo shoot coil so that the diameter of the coil becomes smaller toward the lower end.It is arranged in an inverted position in the can body 7, and the terminal portions at both ends are crowned. The plate 10 and the bottom plate are brazed watertightly. The can body 7 has an inner diameter slightly larger than the outer diameter of the coil of the sheathed heater 6, and the water inlet pipe 8 is brazed to the lower part of the can body 7 so as to communicate in the tangential direction of the can body 7. The tapping pipe 9 passes approximately through the center of the coil of the sheathed heater 6 and is inserted close to the crown plate 10 of the can body 7, and is brazed on the bottom surface of the can body 7.

The operation of the above configuration will be explained below.
First, when the operating pot (not shown) is opened, water flowing into the can body 7 from the water inlet pipe 8 rises while swirling. Therefore, a swirling flow in the winding direction of the coil and a centripetal flow passing between the layers of the coil are applied to the pipe wall of the sheathed heater 6, and the heated water flows down the tap pipe 9 and is discharged. In other words, water flowing from the inlet pipe 8 until being discharged to the outlet pipe 9 flows through the pipe wall of the sheathed heater 6 with a swirling flow, an upward flow, and a centripetal flow. No. 6 causes no local temperature rise.

Since the coil diameter of the sheathed heater 6 increases upward, the amount of heat received by the flowing water in the can increases as it moves upward, and flows down the hot water tap 9, so the temperature of the hot water rises quickly after hot water starts being tapped.

Furthermore, since the sheathed heater 6 does not cause local temperature over-rise, there is little after-boiling after water is stopped, and there is little dielectric breakdown due to repeated use.

As described above, according to this embodiment, the water entering the can body 7 flows evenly through the tube wall of the sheathed heater 6 with swirling flow, upward flow, and centripetal flow, so that the sheathed heater 6 can prevent local temperature overheating. There is no rise in temperature, and since the hot water that has been heat exchanged in the large diameter portion of the coil of the sheathed heater 6 immediately flows down the hot water tap pipe 9, the temperature of the hot water rises quickly after the start of hot water tap. Further, it has the advantage that after-boiling after water stoppage is small and the durability of the sheathed heater 6 is increased.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

The water flow in contact with the bamboo shoot-shaped sheathed heater is given a swirling flow, an upward flow, and a centripetal flow, and the water is circulated between the coil layers, improving heat transfer and eliminating temperature irregularities in the sheathed heater. This has the effect of increasing the temperature of the water quickly, reducing the amount of after-boiling after the water is stopped, and improving the durability of the sheathed heater.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional heat exchanger, FIG. 2 is a top view of a heat exchanger according to an embodiment of the present invention, and FIG. 3 is a sectional view thereof. 6... Sheathed heater, 7... Can body, 8... Water inlet pipe, 9... Hot water outlet pipe, 10... Crown plate.

Claims (1)

[Claims] 1. A sheathed heater that is coil-shaped and formed so that the diameter of the coil gradually decreases downward, a can housing this sheathed heater inside and having an inner diameter slightly larger than the outer diameter of the coil of the sheathed heater, and a can. A water inlet pipe is installed at the bottom of the can so that water flows in from the tangential direction, and an outlet pipe is opened at the top near the top of the can and is installed in the center of the sheathed heater coil. A heat exchanger for an electric instantaneous water heater, in which the water flow to the outlet pipe passes between the coil layers of a sheathed heater by swirling upward flow and centripetal flow.