Patent Application
20130205615
The present application claims priority on a Canadian patent application filed on Feb. 13, 2014, the serial number of which has not yet been made available.
The present application relates to energy recuperation, for instance with laundry dryers, and to a method and apparatus for the recuperation of heat from hot air exhausted by laundry dryers.
A common type of dryer for laundry operates by blowing heated air through a rotating tumbler in which clothes are tumbled. Upon exiting the dryer, the air is exhausted, often directly to the environment. Other types of specialized laundry dryers—without a tumbler—also exhaust air to the environment.
Exhaust air from dryers is often substantially warmer than the environmental air or the ambient air. Accordingly, energy is wasted to the environment when the dryer air is exhausted. The energy loss may be substantial in some applications, such as in commercial dryers of industrial laundry services. Moreover, in some countries, the air that is fed to the dryer is often quite cold and must be heated substantially to be used in a dryer. Hence, the energy consumption of laundry dryers may be substantial in given conditions, with a non-negligible part of the energy being exhausted to the environment.
It is therefore an aim of the present disclosure to provide a method and an apparatus for recuperating heat from dryers, such as commercial dryers.
Therefore, in accordance with the present application, there is provided an apparatus for recuperating heat from a convection dryer, comprising: an exhaust air conduit having an exhaust inlet adapted to receive exhaust air from a convection dryer, and an exhaust outlet adapted to exhaust the exhaust air; an ambient air conduit having an ambient inlet adapted to receive ambient air, and an ambient outlet adapted to feed the ambient air toward a convection dryer; and a heat exchanger unit having a first conduit portion within the exhaust air conduit and a second conduit portion within the ambient air conduit, the first conduit portion and the second conduit portion being arranged concurrently in a heat exchanger configuration for the ambient air to absorb heat from the exhaust air when passing therethrough; and a filtering device in the exhaust air conduit upstream of the heat exchanger unit for filtering airborne residue out of the exhaust air.
Further in accordance with the present disclosure, there is provided a method for recuperating heat from a convection dryer, comprising: receiving exhaust air from a convection dryer; receiving ambient air; filtering airborne residue out of the exhaust air; heating the ambient air by passing the exhaust air and the ambient air in a heat exchanger for the ambient air to absorb heat from the exhaust air; and feeding the heated ambient air toward the convection dryer.
Referring to the drawings and more particularly to
The temperature of the exhaust air varies in accordance with the moment of the drying cycle at which air is exhausted from the dryer. For instance, at the start of the cycle, clothes in the dryer have a greater level of humidity and are colder whereby the exhausted air is relatively colder. Towards the end of a drying cycle, the clothes are dryer and warmer whereby the exhaust air is at a higher temperature. Some dryers also operate cooldown sub-cycles at the end of a drying cycle and the exhausted air is relatively cold during this sub-cycle. As the dryer is used to remove moisture from clothes, the relatively humidity of the exhausted air may be high. Therefore, the apparatus 10 has a controller (i.e., a processing unit) that may control the operation of the apparatus 10 as a function of the drying parameters, as set forth below. The controller may include various types of temperature and pressure sensors measuring the drying parameters.
Referring to
A filtering device 14 is used to remove any residue from the exhaust air. Despite the fact that dryers are often equipped with lint filters, it may be desired to have an additional filtering device as the air will be subsequently circulated to the heat exchanger 16. Heat exchangers 16 comprise narrow passageways in which air circulates, to optimize the heat exchange with fresh air. Airborne particles may obstruct such narrow passageways, resulting in an efficiency loss in the heat exchanger and/or a pressure build-up upstream of the heat exchanger 16. Accordingly, the filtering device 14 provides an additional level of filtration to remove airborne residue that could otherwise affect the efficiency of the heat exchanger 16. The filtering device 14 may be a self-cleaning filtering device to reduce the amount of maintenance required on the apparatus 10.
The heat exchanger 16 is used to perform a heat exchange between the fresh inlet air and the exhaust air from the dryer A. According to an embodiment, the exhaust air and the fresh inlet air do not come into contact. The exhaust air from the dryer A releases heat to the inlet air, thereby warming up same. However, considering that the exhaust air and the inlet air are in a heat-exchange relation but do not come into contact, the inlet air does not absorb humidity or moisture from the exhaust air.
A vacuum 18 is connected to the filtering device 14 to operate vacuuming cycles to remove any residue on the upstream side of the filtering device 14. The vacuum 18 may be operated when a pressure differential above a given threshold is detected across the filtering device 14.
Now that the various stages of the apparatus 10 have been described, a method of operating same to warm up fresh inlet air is described. The apparatus 10 may operate as set forth in the present disclosure by way of the controller operating numerous temperature-, humidity- and/or pressure-measuring devices, installed in the apparatus 10 and in its surroundings (e.g., to measure outside air temperature, exhaust air temperature, etc.) with the measurements used to control the actuation of the apparatus 10. Moreover, the controller of the apparatus 10 may be connected to the processor of the dryer A for concurrent operation, and receive information of the portions of the drying cycle in operation. The controller of the apparatus 10 will actuate various components of the apparatus 10 to maximize the amount of energy recuperated from the dryer A.
According to an embodiment of the method, when a temperature difference above a given threshold is sensed between the air exhausted by the dryer A and the inlet air, a recuperation operation may be performed. The bypass 12 is closed so as to direct exhaust air to the filtering device 14.
In the filtering device 14, airborne residue may be removed from the exhaust air. The exhaust air is then fed to the heat exchanger 16 concurrently with fresh air typically coming from outdoors. In the heat exchanger 16, the exhaust air releases heat to the inlet air whereby same is warmed up. The warmed-up air may then be fed to the dryer A, which will further heat the inlet air to a suitable temperature to be used for clothes drying.
When a differential pressure across the filtering device 14 is above a given threshold, vacuum 18 may be operated to remove residue from the screen of the filtering device 14. During vacuuming, the bypass 12 may be opened to exhaust air. When the exhaust air does not meet recuperation conditions, the exhaust air may be exhausted by the opening of the bypass 12.
Now that the apparatus 10 has been generically described, as well as a method of operation thereof, an embodiment of the apparatus 10 is shown in greater detail. Referring concurrently to
As generally shown in
Referring to
Referring concurrently to
An exhaust air outlet 35 is provided on an opposite side of the casing 20. The exhaust air outlet 35 may also comprise a damper unit 36 similar to the damper units 27 and 32. Accordingly, exhaust air during a recuperation operation goes from the exhaust air inlet 30 to the exhaust air outlet 35 (along stream 22), and passes through the filtering device 14 and the heat exchanger 16 in the process.
Referring concurrently to
A vacuum manifold 42 extends the full length of the filtering device 14, and has a slit facing the screen 41. A pipe 43 is connected to a rear end of the vacuum manifold 42 so as to be connected to the vacuum 18 (
The vacuum manifold 42 is pivotally mounted to the structure 40 by arms 44 securing the vacuum manifold 42 to a pivot 45. An actuator unit 46 actuates the pivoting movement of the vacuum manifold 42 for the vacuum manifold 42 to move up and down along the screen 41 to remove residue therefrom.
Referring to
It is pointed out that there may be moisture build-ups on the heat exchanger 16, whereby the casing 20 may be provided with a draining system for both the exhaust air stream 22 and the inlet air stream 23. The draining system collects moisture by way of a gutter at the bottom of the heat exchanger and drains the moisture away from the apparatus 10.
According to an embodiment, the streams may be induced by the dryer A, with the apparatus 10 not adding blowing actuation to the streams. In relying solely on the convection dryer A to create the air streams, the energy consumption of the apparatus 10 is minimized. It may also be considered to add fans within the casing 20 to create the streams, for instance to optimize the heat exchange between streams.
The reclaim of heat from the exhaust air reduces energy consumption. Moreover, by feeding preheated air to the dryer A, the drying cycle time may be reduced, thereby causing an increase in load capacity of the dryer A.
