Patent Description:
Evaporators utilize latent heat of a fluid to absorb waste heat from a heat source. As such, in order to operate efficiently, an evaporating surface of an evaporator should be covered by a layer of a liquid phase of a working fluid as much as possible during operational conditions. <CIT> discloses an evaporator assembly according to the preamble of claim <NUM>.

The liquid phase of a working fluid (i.e., liquid) tends to accumulate and move in the direction of gravity in a terrestrial environment. In a microgravity environment, liquid distribution is randomized and tends to move freely if undisturbed. Therefore, in each of these terrestrial and microgravity environment cases, it is often critical to replenish evaporating surfaces of evaporators with liquid.

According to invention, an evaporator assembly according to claim <NUM> is provided.

The second end of the perforated tube may be located in the outlet header.

The second end of the perforated tube may be sealed off.

The plurality of orifices may extend circumferentially around the perforated tube.

The plurality of orifices may extend longitudinally along a selected length of the perforated tube.

The selected length may be less than or equal to a length of the evaporator body.

The plurality of orifices may start proximate the adapter and terminate before the outlet header.

The plurality of orifices may extend helically around the perforated tube.

The plurality of orifices may be arranged circumferentially around the perforated tube at a plurality of locations longitudinally along a selected length of the perforated tube.

A fluid pump may be fluidly connected to the inlet header, the fluid pump being configured to deliver a working fluid at a selected pressure to maintain the working fluid through an entirety of the perforated tube.

Movement of a working fluid of an evaporator in a microgravity environment is mainly dictated by a surface tension of the working fluid, characteristics of a surface the working fluid is intended to be in contact with and external disturbances applied to the system. In a terrestrial environment, the working fluid will tend to pool and flow in the direction of gravity. In either case, in a properly designed groove, working fluid can be replenished into the groove and vapor can be expelled out of the groove at similar rates which is useful in the replenishment of working fluid on an evaporating surface of an evaporator. As such, as will be described below, a groove geometry in which working fluid can be replenished into the groove and vapor can be expelled out of the groove at similar rates in integrated into an evaporator design. The evaporator design, according to one or more embodiments, is therefore suitable for both terrestrial and microgravity environments.

Additionally for a long evaporator oriented against gravity or under an adverse acceleration load, the working fluid may not be able to wet the entire length of the evaporator, and thus the evaporator will not have the designed efficiency of the temperature uniformity. The embodiments disclose herein seek to correct this inefficiency by allowing the working fluid to wed the entire length of the evaporator using a perforated tube installed along the length of the evaporator.

Referring now to <FIG>, an isometric view of an evaporator assembly <NUM> is illustrated, according to an embodiment of the present disclosure. The evaporator assembly <NUM> includes an inlet header <NUM>, an evaporator body <NUM>, and an outlet header <NUM>. The evaporator body <NUM> is interposed between the inlet header <NUM> and the outlet header <NUM> and extends from the inlet header <NUM> to the outlet header <NUM>. The evaporator body <NUM> is the evaporating element of the evaporator assembly <NUM>. A fluid pump <NUM> is fluidly connected to the inlet header at the inlet <NUM>. The pump <NUM> is configured to deliver a working fluid <NUM> to the evaporator assembly <NUM> at a selected pressure. The working fluid <NUM> enters the inlet header <NUM> at an inlet <NUM>. The working fluid <NUM> then flows from the inlet header <NUM> to the outlet header <NUM> through the evaporator body <NUM> in a flow direction <NUM>. The working fluid <NUM> absorbs heat <NUM> from a heat source while flowing through the evaporator body <NUM>. The fluid then exits the outlet header <NUM> through an outlet <NUM> at the outlet header <NUM>.

Referring now to <FIG>, with continued reference to <FIG>, a cutaway view of the evaporator assembly <NUM> is illustrated, according to an embodiment of the present disclosure. The working fluid <NUM> is conveyed from the inlet header <NUM> to the evaporator body <NUM> through a feed tube <NUM>. It is understood that, although discussed herein in the singular tense, the evaporator assembly <NUM> may include multiple feed tubes <NUM>, as illustrated in <FIG>. The feed tube <NUM> is composed of an adapter <NUM> and a perforated tube <NUM>. The adapter <NUM> fluidly connects the feed tube <NUM> to the inlet header <NUM>.

The perforated tube <NUM> may be tubular in shape as illustrated in <FIG>. The perforated tube <NUM> includes a first end <NUM> and a second end <NUM> opposite the first end <NUM>. The perforated tube <NUM> extends within and through a channel <NUM> formed within the evaporator body <NUM>. The perforated tube <NUM> is fluidly connected to the adapter <NUM> at the first end <NUM> such that the working fluid <NUM> may flow from the inlet header <NUM> into the first end <NUM> of the perforated tube <NUM> through the adapter <NUM>. The first end <NUM> is attached to the adapter <NUM>. In an embodiment, the second end <NUM> of the perforated tube <NUM> is located in the outlet header <NUM>, as illustrated in <FIG>. In an embodiment, the second end <NUM> is sealed off or closed, such that no working fluid <NUM> exits the perforated tube <NUM> at the second end <NUM>.

The perforated tube <NUM> extends within the evaporator body <NUM> through a channel <NUM> defined in the evaporator body <NUM>. The evaporator body <NUM> is formed to define channels <NUM> that may be arranged in a linear formation <NUM> across a width W of the evaporator body <NUM>. Each of the channels <NUM> can have a substantially same shape as the others.

The perforated tube <NUM> includes a plurality of orifices <NUM> along a selected length L1 of the perforated tube <NUM>. The selected length L1 may be less than an overall length of the perforated tube <NUM>. As illustrated in <FIG>, the selected length L1 does not extend from the first end <NUM> to the second end <NUM> but rather the selected length L1 is about equal to or less than a length L2 of the evaporator body <NUM>. The plurality of orifices <NUM> start proximate the adapter <NUM> or right after the adapter <NUM> but terminate before the outlet header <NUM>. There are no orifices <NUM> located in a portion of the perforated tube <NUM> that is located in the outlet header <NUM>, as illustrated in <FIG>. In other words, the orifices <NUM> stop or cease to exist once the perforated tube <NUM> enters the outlet header <NUM>. The orifices <NUM> fluidly connect the perforated tube <NUM> to the channel <NUM>. The orifices <NUM> are configured to provide the working fluid <NUM> to the channels <NUM> of the evaporator body <NUM>. The orifices <NUM> are configured to provide the working fluid <NUM> to the channels <NUM> in liquid form, where the heat <NUM> may transform at least a portion of the working fluid <NUM> to vapor form. The working fluid <NUM> then migrates from the channels <NUM> into the outlet header <NUM> at a channel outlet <NUM>. The channel outlet <NUM> fluidly connects the channel <NUM> to the outlet header <NUM>. The adapter <NUM> prevents or blocks the working fluid <NUM> from migrating from the channel <NUM> into the inlet header <NUM>. In other words, the adapter <NUM> fluidly separates the channel <NUM> and the inlet header <NUM>.

In order to ensure that the evaporator assembly <NUM> can operate as efficiently as possible under any gravitational or acceleration load from any direction, the evaporative surfaces within the channel <NUM> of the evaporator body <NUM> may be continuously supplied with the working fluid <NUM> in a liquid phase.

The pump <NUM> (see <FIG>) is configured to deliver the working fluid <NUM> into the inlet <NUM>, then to the inlet header <NUM>, then into the adapter <NUM>, and then into the perforated tube <NUM> at a selected pressure in a liquid form. The selected pressure is high enough to maintain working fluid <NUM> throughout an entirety of the perforated tube <NUM> at all times. In other words, the perforated tube <NUM> is always filled with working fluid <NUM> (i.e., completely filled).

Advantageously, since the perforated tube <NUM> is always filled with working fluid <NUM>, the gravitation and the acceleration loads of any magnitude from any direction will not have any significant effect to the fill condition of the perforated tube <NUM> as long as the pump <NUM> is capable of generating enough pressure head to overcome the total system pressure drop.

Referring now to <FIG>, different patterns of orifices <NUM> are illustrated, in accordance with an embodiment of the present disclosure. It is understood that while two patterns of orifices <NUM> are illustrated in <FIG>, the embodiments disclosed herein may be applicable to any pattern of orifices <NUM>. Some examples for other patterns may include but are not limited to a single row, multiple one-sided rows, partial areal coverage, or any other pattern conceivable by one of skill in the art.

<FIG> illustrates a plurality of orifices <NUM> arranged circumferentially C1 around the perforated tube <NUM> at a plurality of locations <NUM> longitudinally L3 along the selected length L1 of the perforated tube <NUM>. In other words, at each location <NUM> there the orifices <NUM> arranged circumferentially C1 around the perorated tube <NUM>. There may be any number of orifices <NUM> at each location <NUM>. In an embodiment, there may be six orifices <NUM> at each location <NUM>, but it is understood that the embodiments disclosed herein may be applicable to more or less than six orifices at each location <NUM>. The number of orifices <NUM> at each location may be equivalent to a number of grooves <NUM> (See <FIG>) in each channel <NUM>. The orifices <NUM> may be aligned with each groove <NUM> such that working fluid <NUM> from the orifices <NUM> may be directed into the groove <NUM>. The number of orifices <NUM> may vary but there may be enough orifices <NUM> such that the working fluid <NUM> can cover the evaporative surfaces of the channel <NUM>. The orifices <NUM> are sized such that the flow of working fluid <NUM> is high enough to reach the evaporative surfaces of the channel <NUM>. The evaporative surfaces includes the grooves <NUM>. The orifices <NUM> may be intermittently spaced or regularly spaced circumferentially C1 around the perforated tube <NUM> at each location <NUM>. The locations <NUM> may be intermittently spaced or regularly spaced (e.g., D1 is the same between each location) longitudinally L3 along the selected length L1 of the perforated tube <NUM>.

<FIG> illustrates a plurality of orifices <NUM> arranged in helically H1 around the perforated tube <NUM>. There may be one orifices <NUM> at each location <NUM> as the plurality of orifices <NUM> winds helically H1 around the perforated tub <NUM>. In other words, the plurality of orifices <NUM> are arranged in a line that winds circumferentially C1 around the perforated tube <NUM> while traversing longitudinally L3 along the selected length L1 of the perforated tube <NUM>.

Advantageously, the orifices <NUM> within the perforated tube <NUM> can be designed to have any pattern as long as the liquid stream of working fluid <NUM> emanating from the orifices <NUM> can cover the channel <NUM>, which is a heat input surface of the evaporator body <NUM>.

Referring now to <FIG>, with continued reference to <FIG>, grooves <NUM> formed within the channels <NUM> of the evaporator body <NUM> are illustrated, according to an embodiment. The evaporator body <NUM> is formed to define channels <NUM> that may be arranged in a linear formation across a width W of the evaporator body <NUM>. Each of the channels <NUM> can have a substantially same shape as the others and includes grooves <NUM> that are circumferentially arrayed to extend radially outwardly from an open central region <NUM> where the perforated tube <NUM> is located.

Each of the grooves <NUM> has a same shape as the others and is immediately adjacent to neighboring grooves <NUM>. In addition, each of the grooves <NUM> is delimited by first and second interior facing sidewalls <NUM> of the evaporator body <NUM>. The first and second interior facing sidewalls <NUM> are tapered toward each other to form a base B and an apex A. The apex A is opposite the base B and has an apex angle 2β where β is less than <NUM>° minus a solid-liquid contact angle. That is, the apex angle 2β is defined such that, for a fluid flow moving through one of the channels <NUM> in a microgravity environment where a portion of the fluid flow is in a liquid phase and another portion of the fluid flow is in a vapor phase, the portion of the fluid flow in the liquid phase within a particular groove <NUM> of the channel <NUM> will move in the particular groove <NUM> from the base B to the apex A and the portion of the fluid flow in the vapor phase within the particular groove <NUM> will move in the particular groove <NUM> from the apex A to the base B.

Referring now to <FIG>, with continued reference to <FIG>, an operation of the channels <NUM> and the grooves <NUM> in a microgravity environment is illustrated, in accordance with an embodiment of the present disclosure. As shown in <FIG>, in the microgravity environment, once liquid contacts the first and second interior facing sidewalls <NUM> of each of the grooves <NUM>, the liquid moves in the direction from the base B and to the apex A. After vaporization by exposure of the evaporator body <NUM> to heat <NUM>, the vapor is expelled from the apex A toward the base B and to the open central region <NUM> where the perforated tube <NUM> is located.

Referring now to <FIG>, with continued reference to <FIG>, an operation of the channels <NUM> and the grooves <NUM> in a gravity field G1 is illustrated, in accordance with an embodiment of the present disclosure. As shown in <FIG>, the gravity field G1 does not affect the distribution of the working fluid <NUM> to grooves <NUM> of the channels <NUM> because the working fluid <NUM> is pressurized and is directed out of the perforated tube <NUM> towards the grooves <NUM>. Therefore, more heat transfer may occur between the evaporator body <NUM> and the working fluid <NUM> because the working fluid <NUM> is not susceptible to the gravity field G1.

Technical effects and benefits of the features described herein include utilizing pressurized perforated tubes to more equally distribute a working fluid in liquid form across a heat transfer surface of an evaporator in both microgravity environments and terrestrial environments.

Claim 1:
An evaporator assembly (<NUM>), comprising:
an inlet header (<NUM>);
an outlet header (<NUM>);
an evaporator body (<NUM>) defining a channel (<NUM>) fluidly connected to the outlet header;
a feed tube (<NUM>) comprising:
an adapter (<NUM>); and
a perforated tube (<NUM>) connected to the adapter, the perforated tube comprising a first end (<NUM>) attached to the adapter, a second end (<NUM>) opposite the first end, and
a plurality of orifices (<NUM>),
wherein the plurality of orifices (<NUM>) fluidly connect the perforated tube (<NUM>) to the evaporator body (<NUM>) of the evaporator assembly (<NUM>) that extends from the inlet header (<NUM>) to the (<NUM>) outlet header of the evaporator assembly;
wherein:
the adapter (<NUM>) is fluidly connected to the inlet header (<NUM>);
the perforated tube (<NUM>) is fluidly connected to the inlet header (<NUM>) through the adapter (<NUM>), wherein the plurality of orifices (<NUM>) fluidly connect the perforated tube (<NUM>) to the channel (<NUM>), (<NUM>) channel (<NUM>), wherein the perforated tube extends within the characterized in that the channel comprises grooves (<NUM>) respectively delimited by first and second interior facing sidewalls of the evaporator body which form a base and an apex (A) with an apex angle opposite the base (B);
the groove circumferentially arrayed to extend outwardly from an open central region where the perforated tube is located;
the apex angle is 2β and β is less than <NUM>° minus a solid-liquid contact angle; and in that the adapter is configured to block working fluid from migrating from the channel into the inlet header.