Patent Application
20130298422
1. Field of the Invention
The present invention relates to domestic appliances, and particularly to a recirculating dryer that provides high energy efficient drying of laundry.
2. Description of the Related Art
Dryers are widely used in domestic and industrial environments to dry articles of clothing and other laundry. The design of dryers has not changed much since their first introduction. Most traditional dryers continuously draw in ambient air, heat the air, and circulate the heated air through a rotating drum or tumbler containing laundry to be dried. The passage of the heated air through the laundry dries the laundry, and the used air exhausts through an outlet vent to the outside. This is a very effective method of drying wet clothes, but it is very inefficient in terms of energy usage. The used hot air still contains much residual thermal energy that is continuously lost in this process. Unfortunately, most traditional dryers have no means of utilizing or recycling heat energy.
Some efforts have been made to improve energy consumption and usage in dryers. For example, microwave dryers have been introduced that basically use microwave energy to vaporize any moisture in the laundry. While efficient in terms of energy consumption compared to traditional dryers, this type of dryer cannot be used on articles containing metal, such as the buttons on jeans pants and the like, for extended periods of time because of the potential arcing that can occur, which can lead to fires. Thus, microwave drying is typically kept to a minimum, and final drying is performed by convection heating.
Another solution lies in spin dryers. These dryers are simply high rpm (rotations per minute) drums that use centrifugal force to squeeze out moisture. Much like the microwave dryer mentioned above, final drying can be performed by traditional dryers for a net reduction in energy consumption. In some cases, spin dryers are used alone.
Another example utilizes a heat exchanger and condenser integrated into the dryer. In this type of system, the exhaust hot air is circulated through the heat exchanger and cooled by ambient air or water. The water vapor is condensed and drained or collected for later disposal, and the cooled air is fed back into the drying loop. This typical condenser dryer helps reduce accumulation of excess humidity, which can have detrimental effects inside a domicile, e.g., mold. While this type of dryer consumes less energy than traditional dryers, the laundry takes longer to dry because the recirculating air is not as dry as fresh ambient air.
Thus, a recirculating dryer solving the aforementioned problems is desired.
The recirculating dryer includes a housing having an operator control panel and a locking door mounted to a side of the housing. A rotating tumbler for holding the laundry to be dried is mounted inside the housing. Heated air is introduced through an inlet of the tumbler and the outlet is kept closed by a flap. The heated air is recirculated and recycled through the tumbler. The air is reheated back to a predetermined temperature if the temperature falls below a level suitable for drying. A layer of moisture absorbent material surrounds the tumbler to absorb the moisture gathered in the air from the drying process. At drying completion, the flap is opened to vent the used air. A control system controls various features with data from a thermostat and moisture detector.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
The recirculating dryer, generally referred to by the reference number 10 in the drawings, dries laundry with minimal energy consumption by actively preventing continuous energy loss from continuous venting of the used air. Instead of continuous venting, the used air is recirculated in the drying environment. This results in more efficient use of energy input, e.g., for heating, as well as more efficient use of the potential thermal energy within the used air.
As shown in
The interior of the housing 12 includes a rotating drum or tumbler 20 where laundry is placed for drying. The tumbler 20 includes an air inlet end and an air outlet end for introduction and exhaust of the air. Additionally, the tumbler 20 can be provided with a plurality of perforations for the air to escape and funnel into the outlet end. A layer of moisture absorbent layer 22 is placed at select locations around the tumbler 20, over perforations, or all around the tumbler 20. The moisture absorbent layer 22 is preferably constructed from material that is highly absorbent, yet resistant to heat. A variety of different materials can be used for this layer, such as cellulose acetate derivatives, polymers and the like. The moisture absorbent layer 22 can also be placed in an outer drum (not shown) to create an insulating effect. The outlet end includes an actuable gate, flap or vent 24 that remains closed during the majority of the drying cycle.
In use, ambient air is initially heated to a given temperature and introduced into the tumbler 20 as indicated by arrow 21. The flap 24 remains closed. The heated air can be introduced continuously, intermittently, or as needed. Unlike conventional dryers, this air is recycled and recirculated during the drying process in order to take advantage of the latent thermal energy or heat that have not been used to dry the laundry during a single cycle or pass of a volume of air.
As the heated air circulates inside the tumbler 20 (shown by arrows 23), the hot air extracts moisture from the wet laundry, which causes the temperature to drop a certain amount. The drying efficiency of the moisture-laden air diminishes due to the moisture content. To compensate, the moisture is absorbed by the moisture absorbent layer 22 throughout the whole process. When a certain level of moisture has been absorbed, the layer is squeezed of its moisture either from direct centrifugal force from the tumbler 20, by mechanical means (not shown), or manually. The moisture can be collected in a collection bin or drained.
When the temperature drop reaches a predetermined level unsuitable for drying, the recirculating air is reheated back to the initial given level. This process continues until expiration of a timer, or to a user-defined level of dryness. The flap 24 is actuated and the used air is allowed to vent, as indicated by the arrow 25. The lint produced from the drying process can be collected and discarded in a manner well known in the art.
The above operations and others are all controlled by the control system 30 operatively connected the operator control panel 16. As shown in
Unlike traditional dryers, the recirculating dryer does not continuously heat the ambient air supply, especially not the air recirculating during the drying process. This substantially reduces energy demand because the amount of energy required to heat the already heated air back to the predetermined level is much less than heating ambient air being continuously fed into the tumbler 20, since the temperature differential is much smaller.
In order to properly determine when additional heating is required or to determine the amount of moisture within the tumbler 20, the control system 30 includes a thermostat 40 for monitoring temperatures and a moisture detector 38 for monitoring the moisture content. The data from these sensors insure that the heater 34 is operating only when needed in order to minimize energy usage, and to determine whether the moisture-absorbent layer 22 is operating at capacity. In the case of the latter, such data can also help determine the necessity of maintenance and/or replacement.
Thus, it can be seen that the recirculating dryer 10 is highly energy efficient, both with the energy required to operate and the energy used in the drying process. The control system 30 insures that only the required amount of energy is being used to heat the air and rotate the tumbler 20. Instead of venting all the hot air passing through the tumbler 20, the hot air is recirculated and reheated as needed, which maximizes the use of thermal energy. The absorbent layer 22 insures that moisture within the drying system is kept to a minimum so that it will not impact drying efficiency.
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.
