Development and design of clothes dryer program

2021-01-05 16:35:53 hongling

Clothes dryers are also called household clothes dryers, which are a very common application in household appliances. Dryers can be divided into two types, industrial and civilian. Industrial dryers are also called drying equipment or dryers. Civil dryers are a type of washing machine. They are generally used to remove clothing and other textiles after water is washed away. Of moisture.


With the fast pace of urban life and the improvement of living standards. For families living in cities, a dryer is becoming more and more necessary. It helps everyone to wear dry and comfortable clothes in winter or rainy weather. Although the simple clothes dryer is a very simple and cheap household equipment, the price ranges from tens of yuan to one or two hundred; but because of its safety, convenience and easy storage, it has been widely used in e-commerce Many sellers also have thousands of sales. The process of drying clothes involves many physical processes, such as convection diffusion, water evaporation, and fluid heat transfer. Research in these areas also has practical significance.


1. The structure of the clothes dryer

A common lightweight clothes dryer on the market consists of a host, a clothes drying rack and a sealing cloth cover.


The host is composed of inner filter, fan and PTC heating element. The host is installed at the lower position of the clothes rack, and the air inlet of the host has a certain space from the ground. After the clothes are hung on the drying rack, cover the airtight cloth cover on the drying rack, and the air outlet of the host is located at the bottom of the airtight cloth cover. The top of the sealing cloth cover has an air outlet.


2. The drying principle of clothes dryer

The fabric to be dried is mainly composed of fabric fibers (in this article, cotton fibers) and moisture. At the beginning of drying, the host provides dry hot air, which raises the temperature of the fabric to be dried on the one hand, and on the other hand, the dry hot air takes away the moisture on the surface of the fabric. Due to the evaporation of surface moisture, there is a difference in humidity between the surface and the inside of the fabric. Driven by this humidity difference, the internal moisture will diffuse to the surface.


Through the simulation of various physical phenomena in the drying process of the clothes dryer, we can more intuitively understand the process of clothes drying. Temperature, wind speed and the moisture contained in the clothes interact with each other, causing the moisture content of different parts of the clothes to change at different speeds.


For manufacturers of simple clothes dryers, how to make the dry hot air at the air inlet be fed from the bottom as evenly as possible is the key to improving the efficiency of drying clothes. A large amount of ineffective dry hot air is lost from the path of least resistance. In terms of design, appropriately increasing the circuitous path or adding a diffuser at the air inlet can make the hot air as uniform as possible.


For families who have bought and used simple clothes dryers, placing the most difficult-to-dry clothes in the nearest place from the air inlet is the best choice. At the same time, consider how to place the clothes so that the clothes do not obstruct the flow of air as much as possible.

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3. Which one is better to use a washer-dryer or a clothes dryer?

After entering March, the weather in the south gradually became humid. After washing clothes, it becomes more difficult to dry them naturally. At this time, a household clothes dryer is very useful. But in the face of all-in-one washing and drying machines and dryers in the market, which one is really suitable for entering the home? What are the essential differences between them?


1. From the area of view


Even though domestic house prices have stabilized a bit recently, they are still at the level of an inch of gold. Especially in the design of many bathrooms, the washing machine can not fit, let alone the extra clothes dryer.


At this time, the space occupied by the washing and drying machine has obvious advantages compared with the combination of "washing machine + dryer". However, many dryers matched with washing machines can be stacked on top of each other with special brackets. Therefore, for families with no height restrictions, there is not much difference in floor space between a stand-alone clothes dryer and a washer-dryer.


2. From the perspective of volume


Washing machines use kilograms as the unit of volume, which is commonly referred to as kilograms. As a clothes dryer matched with the washing machine, the capacity is also measured in kilograms. In general washing and drying machines, the rated weight of washing and the rated capacity of drying are not the same. Take the entry-level product as an example. Generally, for products with a rated capacity of about 8kg, the rated capacity for drying is about 4kg or 5kg. What effect does this have? It means putting in a pile of dirty clothes at a time. Although they can be washed clean at one time, they are not completely dried out and they are still wet. And using a washing machine to wash sheets, quilts, curtains, etc., can not be completely dried to the level that can be used directly.


As for the independent clothes dryer, the rated capacity is usually larger. Therefore, most people feel that the integrated washing and drying machine does not dry, but the independent product is fine. In fact, if you buy a high-end washing and drying machine, the rated capacity of drying will also increase, and the effect is not worse than that of an independent one.


3. From experience


In fact, the user experience can be viewed from several angles, such as the drying speed, the drying effect, the degree of cumbersomeness, and the wrinkles of the dried clothes.


(1) In terms of speed, both are very slow, a single drying is basically more than 2 hours, and a wash is about half an hour.


(2) In terms of drying effect, the problem of rated capacity will cause low-end washing and drying integrated machines to fail to dry clothes completely. High-end products and independent products have better effects, but the price of high-end washing and drying machines is relatively high.


(3) In terms of cumbersomeness, the washing and drying machine is definitely better. After all, the dirty clothes are thrown in, and they can be worn after shaking them out.


(4) In terms of the wrinkles of clothes, independent products are more dominant. But in fact this is not the reason for the model. Since the clothes will be compressed vigorously during the spin-drying stage, the fibers of the clothes directly dried at this time are bent and shaped. The independent clothes dryer has a process of taking it out of the washing machine and shaking it. In this process, the fibers of the clothes are relatively flat, and the clothes will not be too wrinkled after drying. However, the washing and drying machine can achieve a similar effect by taking it out and shaking it off after washing, and then throwing it back into the washing machine and drying it again. In addition, most washing and drying integrated machines do not have a fluff collector. If fluff accumulates in the washing machine and is affected by humidity and high temperature, it is easy to produce mildew. Most of the independent clothes dryers have fluff collectors.


4. From the price


The price of mainstream 8kg domestic clothes dryers is around 4000-6000 yuan, the price of mainstream 8kg washing machines is around 3000-4000 yuan, and the total price of the two is around 7000-10000 yuan. The price of an 8kg washing and drying machine is around 4000-8000 yuan. Therefore, the washing and drying machine product has a more price advantage, but the drying effect will have a certain impact. The price of a high-end washing and drying integrated machine product that has no effect on the drying effect and takes up a small space is about 12,000 to 15,000. When the same effect is achieved, the overall price of a stand-alone product is higher.


To sum up: if you have poor money or space, choose a low-end washer and dryer; if you don’t have money or space, you can choose a high-end washer and dryer; if you don’t have money or space, you should choose an independent dryer; no If you are short on money and not short on space, you can choose at will according to your mood.


Fourth, the drying process analysis of the clothes dryer

By observing the drying process, it can be found that according to the characteristics of the fabric surface temperature and the rate of water loss, the entire process from wetting to drying of the fabric can be divided into the heating stage, the constant-speed drying stage, the reduced-speed drying stage, and the blowing of cold air. stage.


1. The heating stage refers to the stage where the wet fabric adjusts its own temperature in the environment and the moisture content is almost unchanged. This is because at this stage, the temperature of the fabric is low, which is not enough to provide the energy required for a large amount of evaporation of the fabric, so the moisture migration rate is very slow, and the energy provided by the heating wire power is mainly used to increase the temperature of the fabric instead of the moisture in the fabric Lost. The water removed at this stage is mainly free water (water adsorbed on the surface of the fabric).


2. The constant-speed drying stage refers to the stage where the fabric temperature is basically unchanged and the moisture content decreases at a constant rate. It is the main dehydration stage of drying. At this stage, the energy provided by the heating filament is mainly used for the migration of moisture in the fabric, and the energy provided by the dryer to the fabric is equal to the energy required for the evaporation of the fabric. Throughout the process, the fibers on the surface of the fabric are surrounded by water molecules and are always in a saturated state. The moisture removed is mainly the free water existing on the surface of the fabric, the voids between the yarns, and the voids between the fibers. The migration rate depends on the external environment, that is, from the surface of the material. The rate of water vaporization is determined. Moreover, the driving force for mass transfer is the difference between the density of water vapor on the surface of the fabric due to violent evaporation and the density of water vapor in the surrounding moist air (the difference between internal and external water vapor pressure). Therefore, at this stage, the drying efficiency can be improved by changing the external conditions, that is, using high wind speed and large air volume to take away the vaporized water vapor on the surface of the material during the drying process.


3. The deceleration drying stage refers to the stage where the surface temperature of the fabric increases significantly and the rate of decrease of the moisture content of the fabric gradually decreases. At this stage, the surface of the fabric is no longer saturated, and evaporation begins to enter the interior of the fabric. The water removed at this stage is mainly free water molecules existing in the gaps between the fibers, and the migration rate depends on the diffusion rate of water inside the fibers. If overheated, the hydrogen bond and Van der Waals force-based binding energy will be destroyed, resulting in capillary water (water in the internal voids of the fiber) and bound water (water molecules bound to the fiber macromolecules through chemical bonds or hydrophilic groups). evaporation. The rate at this stage is significantly related to the outward migration rate of moisture inside the fabric, so the drying rate is obviously limited by the type of drying fabric and the heat and mass transfer rate of the material itself.


6. The cold air blowing stage refers to the stage in which the temperature and humidity balance between the fabric and the environment is realized. This stage basically does not involve the migration of water, but the temperature drops rapidly.


To sum up, each stage plays a different role in the fabric drying process, the type and quality of moisture to be removed are different, and the drying mechanism and drying rate are also different, so each stage needs to be supplied The energy, drying temperature, residence time of wind speed, and the movement state of clothes are different. They should be controlled separately according to actual needs to achieve the purpose of drying clothes quickly and efficiently. Therefore, it is unreasonable for the dryer to adopt a drying mode with fixed parameters throughout the process, and a mode that adjusts the drying parameters in real time according to the drying stage should be adopted. Therefore, a staged drying mode of positive and negative alternating rotation that makes full use of the temperature, humidity and movement characteristics of the fabric in the fabric drying process is proposed to maximize the drying efficiency of the dryer and try to achieve the overall energy saving of the dryer.

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V. Analysis of drying mode of household clothes dryer

There are three drying modes for the warm air dryer: alternating forward and reverse rotation drying in stages, single direction rotation and stage drying, and single fixed drying.


The drying energy consumption of the phased drying mode with alternating positive and negative rotation is the smallest, followed by the drying energy consumption of the unidirectional rotation phased drying mode, and the drying energy consumption of the single fixed drying mode is the largest. Compared with the single fixed drying mode, the single-direction rotating and staged drying mode saves 5.43% of the drying energy consumption, and the positive and negative alternate rotation staged drying mode saves 12.77% of the drying energy. This is because: the staged drying mode can reasonably adjust the drying parameters according to the stage of drying, avoiding the energy used to increase the temperature of the fabric excessively, and maximizing the energy utilization rate of each stage. The following is a comparison of the pros and cons of the three Hongan models.


1. Comparison of drying time


Among the three drying modes, the drying time of the phased drying mode with alternating positive and negative rotation is the smallest (saving time by 10%), the drying time of the single fixed drying mode is the second, and the drying time of the single-directional rotating phased drying mode Maximum drying time. Comparing the drying parameter settings of the three drying modes, it is found that compared to the drying parameters of the single-directional rotating and staged drying mode, the heating wire power of the entire drying process of the single fixed drying mode is 4 000W, which is higher High, the drying airflow carries more energy, which is beneficial to the evaporation of moisture in the fabric, so the drying time is shorter. And the parameter setting of the whole process of the positive and negative alternating phased drying mode is the same as the one-way rotating phased drying parameter setting, but it adds the positive and negative alternating rotation, and the fabric will not appear single-directional rotating entanglement or clumping. The contact area between the fabric and the drying airflow is increased, the drying thickness of the fabric is reduced, the drying efficiency is higher, and the drying time is shorter.


2. Comparison of drying effect


The final moisture content of the single fixed drying mode among the three drying modes is the lowest. This is because the fabric temperature in the later drying stage of this drying mode is the highest, which makes the internal moisture evaporate more fully, so the final moisture content is the lowest. In the staged drying mode, the surface temperature of the fabric in the later stage of drying is lower, and it is difficult for the internal bound water to migrate fully, so the final moisture content is higher.


3. Comparison of drying uniformity


Among the three drying modes, the drying uniformity of alternating positive and negative rotation and staged drying is the best, and the drying uniformity of the single fixed drying mode and the single-directional rotation staged drying mode is poor, and there are differences between the two Not big. This is because it is easier to shake off the fabric by alternating positive and negative rotation, and the fabric is heated more uniformly, so the drying uniformity is better.


Six, the most suitable drying mode selection for the dryer

From the above analysis, it can be seen that adopting a suitable drying mode can significantly improve the drying efficiency of the dryer, the environmental and economic impact, and improve the appearance of the fabric after drying.


During the whole drying process, the surface temperature of the fabric and the moisture content of the fabric have obvious time-varying and staged characteristics. And according to the fabric surface temperature and the instantaneous moisture content change characteristics of the fabric, it can be divided into a heating stage, a constant-speed drying stage, a reduced-speed drying stage, and a cold air blowing stage. And the main role of each stage is different. The heating stage is mainly to increase the temperature of the fabric at the fastest heating rate; the constant-speed drying stage is mainly to remove 60% to 70% of the moisture in the fabric at the maximum water loss rate, which is the main stage of drying; The stage is to remove as much moisture as possible from the fabric under the premise of ensuring that the surface temperature of the fabric does not increase too much; the cold air blowing stage reduces the surface temperature of the fabric to room temperature at the fastest rate. Therefore, it is necessary to make full use of the characteristics of each stage to carry out staged drying with variable parameters to maximize the drying efficiency.


The drying efficiency and post-drying performance of the alternating positive and negative phase-changing drying mode are significantly better than the drying efficiency and post-drying performance of a single fixed drying mode, and are slightly better than the drying efficiency of the single-directional rotating phased drying mode. Dry efficiency and fabric performance. Compared with a single fixed drying mode, the drying time can be reduced by 10%, the drying energy consumption can be reduced by 15%, the flatness can be increased by one level, and the CO2 emissions and use costs can be reduced.


The alternating positive and negative phased drying mode can not only achieve energy-saving, high-efficiency, environmentally friendly, and non-damaging drying purposes, but also provide a reference for dryer manufacturers to set drying procedures reasonably.