Cooking box functioning with an external source of hot air

A cooking box functions by the supply of an external source of hot air with a temperature higher than 100° C. This external source of hot air is preferably a solar thermal collector of a flat-plate type or CSP (concentrating solar power) type. Auxiliary details in the cooking box allow to achieve high heat transfer parameters from the hot air to cooking utensils placed in the cooking box. The cooking box can comprise a PCM heat storage system for the application of stored heat for cooking or heating food, when the external hot air is not supplied.

BACKGROUND OF THE INVENTION

More than a quarter of the world's population relies on dung, wood, crop waste, or coal to meet their basic energy needs. However, according to the United Nations, about one-third of the world-two billion people-now suffer fuelwood shortages, which means it is harder to find and more expensive. Women, and sometimes children, must walk further distances to find fuel for the family. Some urban families spend 30-50% of their income on cooking fuel or must barter away food for fuel to cook the remainder.

As a result, families drop the nutritious foods that require lengthy cooking—such as vegetables—from their diet, contributing to malnutrition.

Solar cookers prevent deforestation.

Cooking is the main source of demand for wood fuel and can be a major cause of deforestation.

Deforestation contributes to climate change, floods, and soil erosion, increasing environmental degradation, and increasing poverty and hunger.

Each solar cooker in sunny, arid climates can save one ton of wood annually. Meanwhile, with solar cookers families often reduce fuel wood needs by half.

Solar cookers prevent pollution.

Burning fuels such as wood and gas pollute the air and contribute to climate change. Solar cookers provide a pollution-free alternative.

Cooking and heating on open fires or stoves without chimneys leads to indoor air pollution. Every year, indoor air pollution is responsible for the death of 1.6 million people.

Patent EAP 022804 describes a solar heat collector filled with heat storage and conducting material that transfers the solar heat to a heat-insulated range through a heat-transferring medium for cooking foods in utensils and heating water.

However, this patent describes a very complicated cooking system with the application of heat pipes for transferring heat from the solar collector section to the cooping section.

Patent GB 2484353 describes a solar oven for cooking purposes comprised an oven body covered in reflective material, a cooking surface, a lid, a heat storage unit, and a circulatory fan, where the lid is shaped with a mixture of concave and convex portions. Preferably, the heat storage unit comprises a chamber filled with an ionic liquid or a chamber filled with a gaseous or liquid hydrocarbon. Alternatively, the heat storage unit may comprise a solid heat-absorbent material. The heat storage unit may form the surface upon which cooking takes place. Preferably, the temperature within the oven is homogenized by the use of the circulatory fan. The oven may be tiltable upon its base to be positioned in optimum sunlight depending on the position of the sun and the terrain in which the oven is placed. Furthermore, the lid may also be tiltable upon the oven to be positioned in optimum sunlight. Preferably, the cooking surface is either part of the reflective surface or comprises a raised grill situated above the base of the oven.

SUMMARY OF THE INVENTION

This invention proposes a novel design for a solar cooker: a combination of an external source supplying hot air into a cooking box, which plays the role of an oven. The cooking box comprises an external housing, thermal insulation of its lateral walls, a bottom, and an internal housing. A lid with thermal insulation closes this cooking box; the lid is provided with opening appliances, for example with handles on its upper surface.

A flat pedestal is established via a basis plate on the bottom of the internal housing. This flat pedestal comprises several concentric grooves intended for setting removable metal cylinders, which, in turn, serve for setting pots of different diameters. The internal diameter of each removable metal cylinder is larger than the outer diameter of its corresponding pot; in such a way, there is a gap between the pot's outer wall and the internal wall of the removable metal cylinder.

The lower section of each removable metal cylinder is provided with an opening joined with an external pipe branch.

The upper section of the removable metal cylinder can be terminated with a removable neck with an internal diameter that fits the outer diameter of its fitted cooking pot.

In this case, the removable neck is provided with openings to release supplied hot air or another hot gaseous medium.

The outer edge of this removable neck is provided with a skirting directed downwards with the internal diameter, which fits the external diameter of the removable metal cylinder.

To achieve further improvement in heat transfer from the flowing hot air to the cooking pot it is possible to apply a corrugated netting or a corrugated perforated sheet, which is shaped as a removable vertical cylinder with a vertical direction of peaks and depressions of its corrugations, wherein the internal diameter of this removable corrugated cylinder is larger than the outer diameter of the cooking pot and its external diameter is smaller than the internal diameter of the removable metal cylinder.

The internal surface of this removable corrugated cylinder has a high coefficient of absorption/emissivity of electromagnetic radiation in the infrared range of the spectrum.

This removable corrugated cylinder serves as a removable insert, wherein its corrugations serve as spacers and increase additionally the surface of emittance of the infrared electromagnetic radiation.

In another version, the upper section of the removable metal cylinder is terminated with a removable circular tray with a central circular opening, which is provided with an internal skirting directed downwards; this internal skirting has an outer diameter that fits or is less than the internal diameter of the removable metal cylinder.

The external skirting of the removable circular tray, which is directed upwards, is provided with openings for the release of the air.

This external skirting can be designed in a two-stage form, wherein the lower external skirting stage is provided with multiple openings and the upper external skirting stage serves for a pan's positioning for stewing, frying, or other cooking processes.

In addition, this removable circular tray can be used for baking. In this case, the upper external skirting is not provided with openings, but it is applied for positioning a removable circular lid with a central opening to release hot air or another hot gaseous medium. The internal surface of the removable circular lid can be covered with a coating with a high emissivity coefficient in the infrared range of electromagnetic radiation.

To enhance heat transfer from the hot air to the pan's bottom, it is possible to apply a removable insert shaped as a metal disc with multiple perforations, or a metal disc from wire netting.

In both cases, the metal disk has some circular wave-wise deformations or multiple bulges, wherein the heights of these deformations fit the height of the external skirting (or the lower external skirting stage) of the removable circular tray.

The upper surface of the metal disk is covered with a coating with a high emissivity coefficient in the infrared range of electromagnetic radiation.

Application of such a removable insert is desirable if the lower surface of the pan has a high absorption coefficient in the infrared range of electromagnetic radiation.

In an additional version, the upper section of the removable metal cylinder is terminated with a removable rectangular tray with a central circular opening, which is provided with an internal skirting directed downwards; this internal skirting has an outer diameter that fits or is less than the internal diameter of the removable metal cylinder.

The external skirting of the removable rectangular tray, which is directed upwards, is provided with openings for the release of the air.

This external skirting can be designed in a two-stage form, wherein the lower stage of the external skirting serves for a rectangular pan's positioning in stewing, frying, or baking. In this case, the horizontal section of the external skirting is applied to position a removable rectangular lid with a central opening to release hot air or another heating gaseous medium. The internal surface of the removable rectangular lid can be covered with a coating with a high emissivity coefficient in the infrared range of electromagnetic radiation.

To enhance heat transfer from the hot air to the rectangular pan's bottom, it is possible to apply a removable insert shaped as a metal sheet with multiple perforations, or from wire netting.

In both cases, the metal sheet has some corrugation-wise deformations or multiple bulges, wherein the heights of these deformations fit the height of the removable rectangular tray's external skirting (or the lower external skirting stage).

The upper surface of the metal rectangular sheet is covered with a coating with a high emissivity coefficient in the infrared range of electromagnetic radiation.

Application of such a removable insert is desirable if the lower surface of the rectangular pan has a high absorption coefficient in the infrared range of electromagnetic radiation.

There is an inlet pipe branch that is installed at the lower section of the external and internal housings via the thermal insulation and protrudes inwards and outwards relating the internal and external housings.

In addition, one wall of the cooking box is provided with an opening, which can be terminated with an external pipe branch intended to recirculation hot air into its source. The flat pedestal is provided with a radial groove, which allows the establishment of the pipe branch of the removable metal cylinder aligned with the inlet pipe branch of the cooking box.

The lower external surface of each removable metal cylinder is provided with a projection with a width, which fits the width of the radial groove of the flat pedestal. It allows the establishment of the removable metal cylinder in the right position relative to the second branch pipe.

A displaceable connection pipe serves for the fluid communication of the inlet pipe branch and the pipe branch of the removable metal cylinder.

This displaceable connection pipe is provided preferably with a bellows section.

In another version, this displaceable connector pipe can be manufactured from nonpermeable fabric that is terminated with two metal connectors for fluid communication with the inlet pipe branch and the pipe branch of the removable metal cylinder.

The cooking box can be equipped with a means for heat storage for cooking in the cooking box at nighttime when a solar concentrating collector supplying hot air into the cooking box is not functioning.

The upper layer of the flat pedestal is provided in this case with a second radial groove, which is perpendicular to the first radial groove.

It allows the orientation of the removable metal cylinder with its pipe branch toward the internal wall of the cooking box, which is perpendicular to the wall of the cooking box with the second pipe branch.

There is a first rectangular wide bracket, which is installed on this second wall opposite the pipe branch of the removable metal cylinder in its second position.

The first rectangular wide bracket is provided with a circular opening, which is overlapped by a first fan's flange installed on the rectangular wide bracket.

The opposite flange of the first fan is coupled with a pipe branch, which is intended for fluid communication with the pipe branch of the removable metal cylinder installed on the flat pedestal through the telescopic connection pipe or the fabric pipe terminated with two metal connectors.

There is a bank of sealed flat vessels filled with a phase change material (PCM) with a melting temperature somewhat lower than the temperature of hot air supplied into the cooking box.

These sealed flat vessels are arranged vertically in parallel with a certain gap between them and at a certain distance regarding an internal wall of the cooking box, which is perpendicular to the sealed flat vessels.

The second rectangular wide bracket is provided with a circular opening, which is overlapped by a second fan's flange installed on the rectangular wide bracket. The opposite flange of the second fan is coupled with a trumpet's narrow opening and the size of its wider opening fits the size of the sealed flat vessels' set.

The sealed flat vessels filled with PCM perform charging heat when hot air is supplied into the cooking box and discharging heat when hot air is not supplied and the cooking process should be performed. During both cases, the second fan is activated.

The first fan is activated preferably during the supply of hot air into the cooking box without performing the cooking process and during performing the cooking process without a supply of externa hot air into the cooking box.

The cooking box is provided as well with auxiliary equipment: a small photovoltaic panel, a battery of DC, and an inverter for inverting DC in AC.

DETAILED DESCRIPTION OF THE INVENTION