GB2054115A

GB2054115A - Drawer for dry ice

Info

Publication number: GB2054115A
Application number: GB7930581A
Authority: GB
Original assignee: LERMER APPARATEBAU GmbH
Current assignee: LERMER APPARATEBAU GmbH
Priority date: 1979-07-21
Filing date: 1979-09-04
Publication date: 1981-02-11
Also published as: NL7906126A; DE2929666A1

Abstract

An air line food trolley has at the top a drawer 6 covering substantially the entire cross section of the interior of the trolley, for containing dry ice to cool the contents of the trolley. At the rear bottom edge of the drawer are slits 68. Dry ice in the drawer absorbs heat from air inside the trolley and the resulting cold carbon dioxide vapour issues through the slits 68 and descends inside the back of the trolley, thereby directly cooling the contents of the trolley and assisting convective cooling flow inside the trolley. Because the top of the space inside the trolley is substantially complete closed by the dry ice drawer 6, wasteful heat transfer by air flow under the top wall of the trolley is prevented. <IMAGE>

Description

SPECIFICATION Drawer for dry ice This invention relates to drawers for accommodating dry ice (solid carbon dioxide), for placing in a trolley for transporting food and/or beverages in passenger aircraft.

In civil aviation, it is common practice to transport food arid/or beverages in a trolley comprising a closed container, usually having a single door forming one end of the container, dry ice being placed in at least one drawer in the upper region of the interior of the container. The dry ice acts as a refrigerant for cooling and preserving the contents of the container, which are to be served on board an aircraft. The dry ice is put at the top of the container so that air cooled by contact with the surface of the drawer containing the dry ice will fall because of its increased density, displacing the warmer air elsewhere in the container and causing it to move towards the cooling surface of the drawer.A convective counter-flow is therefore generated inside the container, being guided substantially by the free spaces between the contents of the container, usually separate trays of packages with individual portions of food.

However, the arrangement of the refrigerant in drawers simply in the upper region of the trolley allows currents to form between the upper boundary surface of the drawer and the top wall of the trolley, thereby encouraging heat exchange with the ambient air through the top of the trolley, so that the cooling effect of the refrigerant is partly dissipated without cooling the contents of the trolley and the refrigerant is exhausted unnecessarily rapidly.

Furthermore, known designs of drawer do not take account of the fact that the carbon dioxide vapour formed from the dry ice can itself have a cooling effect. In known drawer and trolley designs, the carbon dioxide vapour is confined in the drawer and its cooling effect is therefore largely dissipated through the top of the trolley.

According to the present invention, the dry ice drawer upwardly bounds the internal space of the trolley, and has apertures along its rear wall adjoining the drawer bottom, substantially through the external edge of the drawer, and/or similar passages in this region.

This arrangement can largely eliminate wasteful temperature-equalising flow above the drawer, and assists the thermally generated flow in the space which is to be cooled, in particular by allowing the dense cold carbon dioxide vapour to flow out of the rear of the drawer into the space to be cooled. The passages for outflow of carbon dioxide vapour arnat the rear of the drawer, so that the flow will not be directly disturbed by opening of the trolley door.

The invention therefore effectively provides an additional means for cooling the interior of the trolley, namely a descending current of cold carbon dioxide vapour and air cooled by it, and this descending flow, being concentrated against the back wall of the trolley, will assist circulation of air within the trolley, thereby further improving heat exchange between the air in the trolley and the dry ice-containing drawer. The cooling effect of the carbon dioxide vapour is therefore fully used within the container, and loss of cooling effect by heat exchange with the ambient air is greatly reduced.

It should be noted that at 00C the density of air is 1.293 kg/m3 whereas that of carbon dioxide is 1.977 kg/m3, greater by a factor of 1.53.

Undesirable circulation over the drawer is substantially eliminated because the dry ice drawer (or drawers if more than one is provided) closes the internal space of the trolley at the top.

In particular, convective flow to the top wall of the trolley is prevented.

Preferably, the passages in the drawer are slitlike apertures extending over substantially the entire width of the drawer.

The drawer can conveniently be made of mouided low-flammability polyurethane foam with an imperforate extenal skin.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a side view of an airline food trolley, the upper region being in section on the line AB of Figure 2, Figure 2 shows the upper region of the trolley with its door open, in the direction X shown in Figure 1, Figure 3 is a plan view of the dry ice drawer of the trolley, and Figure 4 is a section of the bottom of the drawer on the line CD of Figure 3.

Figure 1 shows a trolley 1 for passenger aviation, of standard construction, with an undercarriage 2 and braking means 3 that comply with the usual international aviation safety regulations. The trolley has a rectangular container, of which only one, smaller, side is open, this side being provided with a door 4 which occupies the entire area of this side of the trolley so that when the door is open, the whole of the interior of the trolley is exposed.

The trolley has internal rails 5 at its sides for carrying food trays. At its top, a dry ice drawer 6 is supported on rails 7 and a separating sheet 8.

Together, the drawer 6 and the sheet 8 substantially completely close the top of the storage space within the trolley container. A gap 11 adjoining and parallel to the rear wall 10 of the container is left at the rear of the sheet 8, but the rear of the drawer 6 e'ends over this gap.

Immediately above the drawer 6 is a cover sheet 12 which closes the top of the entire dry icecontaining part of the drawer 6.

The drawer 6 is moulded from low-flammability polyurethane foam with a density of about 500 kg/m3, with an imperforate outer skin. In shape, it conforms to the internal cross-section of the trolley. It has a bottom 61, side walls 62, a rear wall 70, a front cross piece 63, and a transverse wall 65 near the front. The cross piece 63 merges into an insulated handle moulding 64 extending to the front wall 65. At the sides of the handle moulding, oblique walls 66 extend from the front wall 65 to the beginning of the cross piece 63.

To increase the contact area, the drawer bottom has internal grooves 67 extending to the front of the drawer. At each side of the handle moulding 64 these grooves extend to the front of the drawer under the inclined walls 66.

In the rear lower edge region 69 (which is rounded in cross section), where the rear wall 70 meets the drawer bottom 61, there are apertures 68 in the form of slits extending over substantially the entire width of the drawer. These slits open above the gap 11 between the sheet 8 and the back wall 10 of the trolley.

In use, dry ice in the drawer extracts heat from the air inside the cooling chamber 9 of the container, thereby producing convection currents in the chamber. The dry ice is thereby evaporated and the resulting cold dense carbon dioxide vapour issues from the slits 68 and falls along the back wall of the trolley, thereby assisting the convection currents and also transferring coldness directly to the contents of the trolley.

The slits extend obliquely downwards, to deflect the carbon dioxide vapour flow in the desired direction along the rear wall. Preferably, the upper surface of each slit makes an angle of 40 to 600 with the rear wall of the drawer, and the lower surface of each slit makes an angle of 10 to 300 with the drawer bottom. The slits therefore converge, and slope downwards. In the illustrated embodiment, each slit makes an angle of 450 with the inner surface of the rear wall, and 150 with the drawer bottom.

The grooves 67 assist heat transfer between the air in the trolley and the dry ice in the drawer, by increasing the contact surface area between the dry ice and the drawer bottom. As shown, the grooves are formed by indentations in the internal surface of the drawer bottom.

Claims

1. A drawer for accommodating dry ice for placement in the top of a trolley for the transportation of food and beverages in passenger aviation, which drawer is constructed to substantially bound in the upward direction the payload chamber of the trolley and is provided with at least one passage in the region of its rear wall for gas flow from the interior of the drawer into the said chamber.

2. A dry ice drawer as claimed in claim 1 in which the or each passage is an aperture extending through the lower rear edge of the drawer adjoining the bottom of the drawer.

3. A dry ice drawer according to claim 2, characterised in that the apertures are slits.

4. A dry ice drawer according to claim 2 or 3, characterised in that the apertures extend substantially over the width of the drawer.

5. A dry ice drawer according to claim 2, 3, or 4, characterised in that the apertures are disposed at an angle of 100 to 300 to the surface of the drawer bottom and at angle of 400 to 600 to the inner surface of the rear wall of the drawer.

6. A dry ice drawer according to claim 5, characterised in that the apertures are disposed at an angle of 1 50 to the surface of the drawer bottom and at an angle of 450 to the inner surface of the rear wall.

7. A dry ice drawer according to any preceding claim, characterised in that a handle moulding, which is insulatingly separated from the dry ice charge, is formed in the middle of the front end region of the drawer.

8. A dry ice drawer according to any preceding claim, characterised in that the contact surface between the dry.ice and the drawer bottom floor is increased by grooves in the drawer bottom.

9. A dry ice drawer according to any preceding claim, characterised in that it consists of lowflammability polyurethane foam with an imperforate outer skin.

10. A dry ice drawer according to claim 9, characterised in that the polyurethane foam has a density of approximately 500 kg/m3.

11. A dry ice drawer for a food trolley, substantially as herein described with reference to the accompanying drawings.