Evaporator and a method for vaporizing a substance in an evaporator

Abstract

An evaporator (1) for vaporizing a substance into its gaseous form, which comprises a cylindrical outer shell (2) and a plate pack (4) arranged inside the cylindrical shell in its lower part and a droplet separator (9) arranged above the plate pack. A recirculation of a substance to be vaporized is carried out by using flow guides (10a, 10b) arranged tightly between the plate pack and the outer shell and by an ejector pipe (13) arrangement comprising a collection pipe (11) arranged inside the outer shell.

Claims

1. An evaporator for vaporizing a substance in a liquid form to thereby create a gaseous form of the substance, wherein the evaporator comprises at least: an outer casing adapted to contain therewithin the substance in the liquid form, wherein the outer casing comprises a cylindrical shell having a horizontally oriented longitudinal dimension, and first and second vertically oriented end plates which close respective opposed first and second ends of the cylindrical shell, an inlet connection for introducing the substance in the liquid form into the outer casing and thereby establishing a liquid level of the substance in the liquid form within the outer casing, a plate pack which extends in the longitudinal direction of the cylindrical shell and is arranged inside a lower part of the outer casing, inlet and outlet ports for a heating substance each for respectively leading the heating substance into and out from the plate pack to vaporize the substance in the liquid form, an outlet connection for the gaseous form of the substance to lead the gaseous form of the substance out of an upper part of the outer casing, flow guides or plates arranged inside the outer casing between a lower portion of the cylindrical shell and a lower part of the plate pack on both sides of the plate pack, wherein the lower part of the plate pack is positioned under a center line of a crosswise direction of the plate pack, wherein the flow guides or plates comprise first and second ends each positioned in a cross-direction of the outer casing such that the first ends of the flow guides or plates are attached to the plate pack and the second ends of the flow guides or plates are attached to the cylindrical shell, a circulation pipe arrangement positioned so as to guide a part of the substance in the liquid form from inside the outer casing back into the outer casing through the inlet connection for the substance in the liquid form, at least one ejector pipe which is positioned at least partly within the circulation pipe arrangement, a droplet separator which is arranged inside the outer casing above the plate pack, and two collection pipes each being positioned on a respective side of the plate pack below the liquid level of the substance in the liquid form within the outer casing, wherein the collection pipes extend in the horizontally oriented longitudinal direction of the cylindrical shell from the first end plate towards the second end plate, the collection pipes having openings along an entire lengthwise extent thereof which are arranged above the flow guides or plates inside the outer casing, wherein the collection pipes are connected to the circulation pipe arrangement and are arranged to suck the substance in the liquid form from an interior of the outer casing by causing the substance in the liquid form to flow through the at least one ejector pipe positioned at least partly within the circulation pipe arrangement.

2. A method for vaporizing a substance in a liquid form to thereby create a gaseous form of the substance within an evaporator which comprises: an outer casing adapted to contain therewithin the substance in the liquid form, wherein the outer casing comprises a cylindrical shell having a horizontally oriented longitudinal dimension, and first and second vertically oriented end plates which close respective opposed first and second ends of the cylindrical shell, an inlet connection for introducing the substance in the liquid form into the outer casing and thereby establishing a liquid level of the substance in the liquid form within the outer casing, a plate pack which extends in the longitudinal direction of the cylindrical shell and is arranged inside a lower part of the outer casing, inlet and outlet ports for a heating substance each for respectively leading the heating substance into and out from the plate pack to vaporize the substance in the liquid form, an outlet connection for the gaseous form of the substance to lead the gaseous form of the substance out of an upper part of the outer casing, flow guides or plates arranged inside the outer casing between a lower portion of the cylindrical shell and a lower part of the plate pack on both sides of the plate pack, wherein the lower part of the plate pack is positioned under a center line of a crosswise direction of the plate pack, wherein the flow guides or plates comprise first and second ends each positioned in a cross-direction of the outer casing such that the first ends of the flow guides or plates are attached to the plate pack and the second ends of the flow guides or plates are attached to the cylindrical shell, a circulation pipe arrangement positioned so as to guide a part of the substance in the liquid form from inside the outer casing back into the outer casing through the inlet connection for the substance in the liquid form, at least one ejector pipe which is positioned at least partly within the circulation pipe arrangement, a droplet separator which is arranged inside the outer casing above the plate pack, two collection pipes each being positioned on a respective side of the plate pack below the liquid level of the substance in the liquid form within the outer casing, wherein the collection pipes extend in the horizontally oriented longitudinal direction of the cylindrical shell from the first end plate towards the second end plate, wherein the collection pipes are connected to the circulation pipe arrangement and have openings along an entire lengthwise extent thereof which are arranged above the flow guides or plates inside the outer casing, wherein the method comprises the steps of: (a) introducing the substance in the liquid form into the outer casing through the inlet connection to thereby establish the liquid level of the substance in the liquid form within the outer casing, (b) causing the heating substance to flow inside the plate pack between the inlet and outlet ports for the heating substance thereby vaporizing the substance in the liquid form, (c) leading the substance in the liquid form from the bottom of the outer casing into a space between the flow guides or plates within the outer casing, (d) leading the gaseous form of the substance out of the upper part of the outer casing, and (e) sucking a part of the substance in the liquid form from the interior of the outer casing through the collection pipes extending into the outer casing below the liquid level of the substance in the liquid form within the outer casing by causing the substance in the liquid form to flow through the at least one ejector pipe positioned at least partly within the circulation pipe arrangement and circulating the substance in the liquid form back into the bottom of the outer casing.

Description

DESCRIPTION OF THE DRAWINGS

(1) The invention will be described in more detail with reference to appended drawings, in which

(2) FIG. 1 shows a longitudinal cross-section of an evaporator according to an embodiment of the invention with recirculation arrangement, and

(3) FIG. 2 shows a cross-section of an evaporator according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(4) Same reference signs have been used in the Figures for parts corresponding to each other.

(5) FIG. 1 shows a longitudinal cross-section of an evaporator 1 according to an embodiment of the invention with a recirculation arrangement.

(6) The evaporator 1 comprises an outer casing, which is formed of a substantially horizontal cylindrical shell 2 and substantially vertical ends 3a, 3b. A plate pack 4 is arranged inside the cylindrical shell. The plate pack 4 is typically arranged in the lower part of the cylindrical shell and a droplet separator 9 is arranged above the plate pack at the upper part of the cylindrical shell. The plate pack 4 is formed by circular heat exchange plates arranged one on top of each other and the plate pack 4 is arranged inside the horizontal cylindrical shell 2 so that the longitudinal direction of the plate pack is the same as the longitudinal direction of the cylindrical shell. The outer surfaces of the plate pack 4 functions as heat exchange surfaces of the evaporator. FIG. 2 shows also filler unit type of flow guides 10a, 10b arranged between the outer casing of the cylindrical shell 2 and the plate pack 4. The flow guides 10a, 10b are designed such that they eliminate the by-pass flow between the plate pack and outer casing and also reduce the liquid volume of the evaporator part as much as possible. The construction of the flow guides is not limited to a shape presented in FIG. 2, but the flow guides might also be thin plate like structures arranged tightly between the plate pack 4 and the inner surface of the outer shell 2. An inlet connection 7 and an outlet connection 8 are arranged to lead heating substance into and out from the plate pack 4.

(7) An inlet connection 5 for a substance to be vaporized is arranged at the bottom of the cylindrical shell 2 and the outlet connection 6 for the vaporized substance is arranged at the upper part of the cylindrical shell 2 above the droplet separator 9.

(8) The liquid level 14 of a substance to be vaporized, such as the refrigerant or other liquid to be vaporized, is advantageously adjusted to the level of the diameter of the cylindrical shell (shown in the FIG. 2), whereby the surface area of the substance to be vaporized is as large as possible and the production of vapour per surface area is as small as possible. The ascension speed of the vapour is thus also as small as possible, whereby the generated droplets travelling with the vapour more easily fall back down. Thus, the gravitational droplet separation is made more efficient.

(9) From the interior of the outer shell 2, i.e. from a shell side of the heat exchanger, a part of a substance to be vaporized is sucked into the circulation pipe 12 arrangement by using at least one collection pipe 11. At least one collection pipe 11 is arranged above the flow guide 10a, 10b inside the outer casing. Typically, the evaporator 1 comprises two collection pipes 11a, 11b; one collection pipe arranged on both sides of the plate pack 4 above the flow guide 10a, 10b. The collection pipe is arranged below the liquid level 14 of the substance to be vaporized. A collection pipe 11, 11a, 11b comprises openings through which a substance to be vaporized is sucked from the interior of the outer casing. Typically, the collection pipe 11, 11a, 11b comprises openings substantially in the whole length of the collection pipe. As shown in Figures, the collection pipe 11, 11a, 11b has typically a length, which is substantially same as the length of the horizontal cylindrical shell and the collection pipes are arranged substantially horizontally into the outer casing.

(10) The collection pipe 11, 11a, 11b is arranged to guide a part of a substance to be vaporized to a circulation pipe arrangement 12 and back to the inlet connection 5 for a substance to be vaporized. The suction is performed by arranging an ejector pipe 13 at least partly inside the circulation pipe 12, i.e. the circulation pipe and the ejector pipe 13 are arranged within each other. The collection pipe(s) 11, 11a, 11b functions as a suction pipe of the ejector system. The inlet flow of substance to be vaporized is guided through the ejector pipe 13 of the evaporator system according to the invention.

(11) Typically the evaporator 1 is a part of refrigerating machinery, in which it functions as a flooded evaporator and a thereto related droplet separator.

(12) The vaporized substance is guided forward to the compressor from the upper part of the evaporator through the outlet connection 6. The figures do not show a connecting tube from evaporator to the compressor and a connector tube form the condenser to the circulation pipe. The refrigerant from the condenser is guided through the expansion valve into the ejector pipe 13.