Group Engineering Proposal
SCHOOL OF SCIENCE AND TECHNOLOGY, SINGAPORE
INVESTIGATIVE SKILLS IN SCIENCE
Bhakti Choudhary 
Vanshiqa Agrawal 
Zhao Siting 
Type of Research:
[ ] Test a hypothesis: Hypothesis-driven research
[ ] Measure a value: Experimental research (I)
[ ] Measure a function or relationship: Experimental research (II)
[ ] Construct a model: Theoretical sciences and applied mathematics
[ ] Observational and exploratory research
[ X ] Improve a product or process: Industrial and applied research
Title of project:
Development of a Dehumidifier
Problem being addressed
People are sensitive to humidity because the skin relies on air to get rid of moisture. When we sweat, water evaporates through the skin and cools us down. If the air is measured to be at 100% relative humidity, it cannot hold any more moisture. Therefore sweat will not be able to evaporate and air will feel warmer than it actually is and our skin will feel extremely sticky causing us to be hot and bothered. However, if the relative humidity is low, sweat will evaporate very quickly and thus our body will stay cool. For example, if the air is 24º and has a relative humidity of 0% , the air will feel to you like it is 21º. If the relative humidity is at 100%, then the temperature will feel like it is 27º. We feel most comfortable when the relative humidity is around 45%. (Discovery Communications, 2014)
Due its geographical location (1 degree north of the equator) and maritime exposure, Singapore is characterised by a hot and humid climate. Instead of having clear-cut seasons like summer, spring, autumn and winter, the weather is warm and humid all year round causing the relative humidity to be in the range of 70% - 80%. It varies from 90% in the morning and falls to around 60% in mid-afternoon, when it is not raining. Often the humidity level touches a whooping 100% on rainy days. (Janus Corporate Solutions, 2014) Due to the high relative humidity range, we often feel uncomfortable and hot despite the low temperatures. This often robs us of our sleep and prevents us from working to their fullest potential, a quality essential for success in a place like Singapore. Excessive humidity in the air not only causes mold and mildew to grow inside homes, it is also an ideal condition for most pests, such as, clothes moths, fleas, cockroaches, dust mites and woodlice to grow. (Wikipedia, 2014) Also, the relative humidity fluctuates many times throughout the day but Singaporeans, known to having a hectic lifestyle, often find themselves time-bound and unable to leave their work to switch on the dehumidifiers. This will not only make them feel uneasy, but the high humidity will also deviate their attention from their work and they will be unable to deliver the good quality work expected of them. All of these problems boil down to the high humidity rate in Singapore and the busy work lives of Singaporeans.
Singaporeans, known to having a hectic lifestyle, often find themselves time-bound and unable to leave their work to switch on the dehumidifiers. By making it automatic, we are making the dehumidifier easier for people’s use.
Our goal is to make dehumidifiers easier for people to use. Dehumidifiers are generally household appliances that are used to reduce the level of humidity in the air. (Wikipedia, 2014) By using dehumidifiers, Singaporeans can easily get rid of problems stirred up by high humidity levels, namely deprivation of sleep and concentration towards our work and growth of pests and fungi. It will be automatic and will turn on when the amount of humidity in the surrounding atmosphere is higher than a certain level (45% - 50%) and start decreasing the amount of humidity in the air. This way users do not have to lift a finger for the dehumidifier to do its job and this makes it more helpful and suited to the hustle and bustle of Singapore.
- It will turn on when the amount of humidity in the surrounding atmosphere is higher than a certain level (45%).
- Once the level of humidity has been brought down to a certain level (45%) the dehumidifier will automatically switch off.
- Decreases the amount of humidity in the surrounding atmosphere.
3 Different Designs
The Different types of Dehumidifiers
- The Chemical Absorbent Dehumidifiers / Desiccant Dehumidifiers
- Homemade Dehumidifiers
- Heat-pump Dehumidifiers
The Chemical Absorbent Dehumidifier
They are made of silica gel (desiccant), which is a desiccant-type of absorbent. The little packet of silica is situated inside the packaging of any kinds of goods that require the waterproof material against condensation and water damage. On a large scale basis, the silica material can be used to absorb the moisture from the air and dehumidify it. The gel is heated and placed on a wheel (separate loop that dries the gel) and removes damp air through a vent. This process does not need to cool air before removing moisture from it. These dehumidifiers are particularly serviceable if the person's living conditions are extremely warm or humid which is similar to Singapore’s climate. (Tsavo Media Inc, 2014)
A detailed description of how the chemical absorbent dehumidifier works:
Air inside the room flows over to the desiccant material (a hygroscopic substance used as a drying agent) . This attracts the moisture from the air. The desiccant material is concurrently dried by air flowing the opposite way that exhausts the moisture towards to the exterior of the room. This describes the cyclical chemical absorbent dehumidifiers.
A wheel revolves the desiccant material. On one side of the wheel, the desiccant material extracts the moisture from the air. On the opposite side of the wheel, the material is dried through the air flow that extracts the moisture towards the air which is outside the room.
During this process, the chemical absorbent material is contained on a bed. Two different stream, low humidity and high, are passed on to the sealed chambered sections, without mixing the two different humidified air, and hence the desiccant material may be removed and dried at intervals.
Figure 1 - Inside a chemical absorbent dehumidifier (bigclivedotcom, 2013).
Figure 2 - Air flow occurring inside a chemical absorbent dehumidifier (Everything Ice, 2014).
The Homemade Dehumidifiers
As nowadays, the dehumidifiers sold are very expensive, people are able to build their own dehumidifiers called ''Homemade Dehumidifiers'' . However , these dehumidifiers are extremely labor intensive. They are also disparate from the controlled dehumidification processes.
The equipments needed to build this homemade dehumidifier is road salt [ caution: road salt can be detrimental to human skin and can rust off metals ], two buckets, a bit of chicken wire and a stand. A portable hygrometer can also be useful to conduct this experiment.
To create the homemade dehumidifier, firstly, make a hole in the bottom of one of the buckets. Cover this hole with netting or a wire to ensure that the salt doesn't fall out. Then, empty the bag of road salt into the container and place the bucket on a stand. After that, the other bucket goes underneath, it must be deep and wide enough to catch water that is captured and drained out of the bucket that has a hole in into bottom.
By going through a natural process, the road salt condenses moisture from the air in the surroundings. If you want to increase the rate of dehumidification, you can place a fan to blow air into the bucket.
To ensure that the effectiveness of the homemade dehumidifier is appropriate, all the windows and doors are supposed to be closed as the relative humidity is controlled by the temperature that is inside and outside. (Tsavo Media Inc, 2014)
Figure 3 - A homemade dehumidifier
The Heat-pump Dehumidifier
The technique used in this is similar to that of an air conditioner. A fan that draws indoor heat over a heat exchange coil that is reduced to near-freezing temperatures. The water vapour in the air condenses on the coils and is subsequently drained into a tank to be disposed of. Afterwhich, the air is reheated and distributed throughout the room again.
A more detailed explanation:
1. A liquid refrigerant is pumped through coils on the outside end of the heat pump dehumidifier.
Figure 4 - 1st process of a heat pump
2. A fan pulls the air outside over the coils. The water in the coils absorbs the heat in the surrounding and expands hot vapour.
Figure 5 - 2nd process of a heat pump
3. The vapour is then put through a condenser, which increases its pressure and temperature, after which, it flows through the indoor coils.
Figure 6 - 3rd process of a heat pump
4. As it cools, the refrigerant condenses back into liquid and flows outside to collect more heat from the surroundings.
Figure 7 - 4th process of a heat pump
5. Meanwhile, the heat is pumped into air ducts to be distributed throughout the entire house.
Figure 8 - 5th process of a heat pump (Laura & Emilie, 2009).
Different Ideas :
Figure 9 - Rough sketch of Design 1
This is the first design that we came up with. It is operated by Arduino and uses silica gel to dehumidify the air. A long pipe will lead from the bottom of the room to the top of the room. Silica gel will be place halfway inside the pipe. A fan will blow the humid air from the bottom of the room through the pipe such that it flows over the silica gel which will then absorb the moisture from the air. Then the dehumidified air will be blown back into the room. This cycle will continue on until all the air in the room will be dehumidified. In order for the silica gel to not moisten itself and lose its absorption capacity, there will be a heater below it and an opening above it. When the fan is switched off, the heater will be switched on and the cap above it in the pipe will be opened. This will cause the silica gel to heat and the water vapour absorbed will be released. Therefore, the person will not need to keep changing the silica gel. The fan below is to blow the humid air towards the silica gel to dry.
Disadvantages: The pipes may have cracks in them which will cause the dehumidified and humid air to mix and thus the air will not be dehumidified as efficiently.
- Due to the heater, the silica gel can be dried and does not have to be changed again and again.
- The cap, when closed, will allow the dehumidified air to be blown back into the room since the air cannot escape from anywhere.
- The cap, when closed, allows the air, which is moist from the water vapour absorbed from the silica gel, to escape into the outside environment and thus, when the fan is switched on, moist air will not be blown back into the room.
- The arduino can be programmed in such a way that the fan will not be on at the same time as the heater thus only the dehumidified air will be blown into the room if the fan is on. And moist air will not be blown into the room since the fan will not be on when the silica gel is being heated.
Requirements for (A) :
< or equal to 45%
Figure 10 - Requirements for Design 1
Figure 11 - Front view and side view of Design 2 and requirement table.
This is the second design we came up with. As the air gets sucked in by the fan attached in the front of the box, the air will travel through the pipe and enter the wheel. The wheel is divided into two sections.
One of them carries the air with low humidity rate and the other big portion carries the air with high humidity. On one side of the wheel, the desiccant material extracts the moisture from the air. On the opposite side of the wheel, the material is dried through the air flow that extracts the moisture towards the air which is outside the room.
There is an extra pipe attached to the wheel which pumps in hot air. The air from the atmosphere enters that extra pipe and the air is heated up with the help of the heater. This heated air is to ensure that the silica gel in the wheel will stay heated up for it to function properly.
There is another outlet from the wheel that pumps out the moisture extracted from the air. The water now can also be used for other uses. The low humidity rate, which is the dry air from the wheel will then get pumped out of the wheel through another outlet pipe. This dry, processed air will leave the dehumidifier and lessen the humidity in the room.
- There might be cracks in the pipe which will cause the air with different humidity levels to escape into the room and the air cannot be dehumidified efficiently.
- The heat pump will heats the desiccant so it can pass through the wheel to remove moist .
- Since the desiccant wheel is rotating slowly, the entire wheel can be warmed eventually .
- Through the pipe, the moist air can be blown out of the room and it will not be mixed with the dehumidified air.
- Due to the fan, the humid air can be blown into the desiccant wheel and the dehumidified air can be blown out of the wheel and into the room.
Our Chosen Solution
We have chosen to build Model [B] , which is a simplified version of a chemical absorbent dehumidifier. It mainly consists of a desiccant wheel that rotates slowly and absorbs moisture from the air which is blown in through a fan. The desiccant will be simultaneously dried because hot air will be blown into it by a hair dryer at the same time.
The desiccant wheel will be made of a round tin box filled with silica gel. There will be cross-shaped partitioning inside the box so the silica gel does not get collected to one side as the wheel turns. A motor will be connected to the tin box to allow it to revolve. Mesh from a flour sieve will replace the cover of the tin box.
Figure 12 - Round tin box
The desiccant wheel will be placed inside another square tin box. The back and the front of this tin box will have identical holes cut on them, with cross-shaped metal rods placed in front of the holes. Two pipes will be attached to two different sections of the rod, both at the back and the front of the box. One pipe will be attached to a hair dryer while the other pipe will be attached to a fan at the front of the box. The two pipes at the back of the box will serve as exhaust pipes as the humid air from the hairdryer will be blown out of the desiccant wheel into the outside environment to prevent it from mixing with the dehumidified air in the room. The other pipe will allow the fan to blow dehumidified air back into the room.
Figure 13 - Front view, side view and back view of desiccant wheel (from left to right)
A basic description of how the entire dehumidifier will function: The fan will blow humid air through the silica gel which will extract the moisture from the air and the dehumidified air is blown out back to the room through the opposite side of the wheel. In the meantime, the hair dryer blows the hot air into a section of the wheel and this warms up the desiccant as it travels along to maximize its absorption capacity since the warm air allows the moisture to evaporate from the desiccant as water vapour. The moist air is then being blown out of the room, with the aid of a pipe, which leads it to the environment outside. This way the air is dehumidified and the desiccant is dried again so that it will not be repeatedly changed.
A hygrometer is an equipment used to measure the water vapour in the atmosphere or the relative humidity. They usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed. (Wikipedia, 2008) There are a variety of hygrometers such as, simple psychrometers and hair hygrometers or even more complex ones such as a cooled mirror dew point hygrometer. (Kestrel Meters, 2012)
An Arduino, which consists of two parts, the hardware and software, allows users to build close to anything. It is made to be connected to sensors which in turn feed it physical information to act upon. A diversity of sensors can be used, from something as straightforward as pressing a button or something as complicated as using an ultrasound to detect distance between two objects. When there is a change in readings or information, the Arduino will carry out the instructions it is programmed to do. (Charlie, 2008)
Therefore, the hygrometer will measure the relative humidity in the air and when it goes above 50% , the Arduino, which is connected to the hygrometer and humidifier, will be given instructions to switch the dehumidifier on automatically. Similarly, when the dehumidifier decreases the relative humidity back to 45%, the hygrometer, measuring the relative humidity, will instruct the dehumidifier to turn off and thus the relative humidity will not go below the necessary percentage. This will reduce hands-on work required to minimal and thus make the lives of the busy Singaporeans much easier. Another advantage of attaching a hygrometer is that users can also read off it to know the relative humidity in the atmosphere.
> 45 %
< or equals to 45 %
Figure 14 - Requirements for Final Solution
For the Arduino:
- DHT11 basic temperature-humidity sensor x1
- Arduino Black (Leonardo Model) x1
- USB cable x1
To make the dehumidifier:
- Computer fan (12 cm x 12 cm, 480 V) x1
- Glue Guns x2
- Tubes x 2 meters
- Nuts and Bolts x1 packet
- Hair Dryer (220 V -240 V) x1
- Duct Tape x1
- Plastic box x1
- Drill x1
- Swiss Army Knife/ Pen Knife x1
- Saw x1
- Screwdriver Set x1
To make desiccant wheel:
- Tin Box (20.6 cm x 20.6 cm x 6.5 cm)
- Flour sieve x2
- Motor x1
- Premium Silica Gel (Drying Agent), 500 gm x2 bottles
- Nuts and Bolts x4
- L-shaped brackets x4
- Aluminium plates 20.5 cm x 2.5 cm
- Wooden blocks x 4
- Wooden Rod x1
- Rubber belt x1
For the testing:
- Digital Thermo-Hygrometer x 2
- Wooden Box (70 cm x 70 cm x 72cm) x1
- Cling Wrap x 1 roll
1) Building the desiccant wheel :
a) Drill a hole in the center of a round tin box.
b) Glue 4 wooden blocks to the base of the round tin box, using hot glue guns, in a spiral pattern around the wooden rod. Paste duct tape around the wooden blocks or any sides to prevent gaps for air to escape or for silica gel to escape.
c) Draw out 4 holes in each of the partitions to be cut at the bottom of the round tin box.
d) Cut out the holes using a hammer, a nail and snips.
e) Using a pen knife, cut out mesh wire from a flour sieve. Trace the outline of the 4 holes cut out using a permanent marker and cut out the outlines. Cover the holes with mesh,cut out from the flour sieve, using duct tape.
f) Fill the 4 partitions in the round tin box with silica gel.
g) Cut out mesh wire from another flour sieve using a pen knife. Place it on top of the round tin box and mark out the position of the wooden rod. Cut out a hole where the wooden rod will be placed.
h) Cover the top of the round tin box with the mesh wire [from o)]. Snip the edges of the wire mesh using scissors and then use duct tape to secure the wire mesh onto the round tin box. Hammer nails into the wooden partitions of the to nail the mesh wire to them.
i) Attach a motor with a disc to a bracket. Place a rubber belt around the disc of the motor and the round tin box.
2) Building the structure :
a) Sketch out a detailed diagram of the structure, inclusive of all the required measurements.
b) Cut out a wooden rod of length 7.5 cm.
c) Drill holes in the center of the bottom of square tin box and the centre of the round tin box.
d) Sandpaper the wooden rod so it reduces in diameter and can slide into the holes in the center of the box easily.
e) Cut out two L-shaped aluminium brackets from an L-shaped aluminium plate and drill holes into the brackets. File the edges of the brackets to make the blunt and less risky.
f) Cut out two metal plates (21.5 cm x 21.5 cm) and drill holes into the ends of each metal plate. File the holes to remove the excess aluminium around it [ safety ] and to make the hole slightly bigger.
g) Secure 2 brackets to each end of the two metal plates using nuts and bolts. Tighten the screws using a vice clamp and a plier.
h) Place the 2 metal plates, with brackets attached to them, on the square tin box and mark out where to drill the holes to screw the brackets to the tin box.
i) Drill holes in the places marked out and hand-tighten the metal plates to the tin box to make sure it fits. Unscrew the metal plates from the tin box once made sure that all the holes are well aligned.
j) Cut out 4 circles, each of diameter 4.5 cm, from the back of the square tin box
k) Place the round tin box, with the motor attached, inside the square tin box and align the 2 holes in the center of the 2 boxes with each other.
l) Insert the wooden rod into the 2 holes and then screw the 2 metal plates (from h)) on the square tin box after inserting the wooden rod into them. Tightly wound a rubber band around each end of the wooden rod and tape the rubber band down to make sure it does not slide out of the rod.
m) Ensure that the round tin box is able to be spun by the motor by switching the motor on.
n) Place the entire desiccant wheel in the center of a plastic box.
o) Place the motor a few centimeters away from the round tin box and mark out the position of two holes in the bracket of the motor on the base of the plastic box. Remove the motor before drilling holes in the marked-out positions. Replace the motor and screw it to the base of the plastic box.
p) Screw the square tin box to the base of the plastic box by drilling holes in both the tin and the plastic box.
q) Screw steel protections to the back and front of a computer fan.
r) Place the computer fan on the wall of the plastic box such that it faces the front of the desiccant wheel. Trace and cut out the circle of the computer fan. Screw the computer fan to the plastic box such that the front of the fan faces inside the plastic box.
s) Cut the thin end of a funnel of and replace it with a pipe using duct tape. Attach the mouth of the funnel to the computer fan, making sure to cover the entire front of the fan.
t) Tape the pipe [from 4)] to the left side of the metal plates using duct tape such that all the air is directed to the silica gel inside the desiccant wheel.
u) Attach a hair dryer to the right side of the metal plates using duct tape such that all the air is also directed to the silica gel.
v) Cut out an opening in the box for the wire of the hair dryer and the motor to be lead outside the box. Once the 2 wires have been pushed outside the box, seal the opening using duct tape and cardboard.
w) Cut out 4 holes of diameter 4.5 cm in the wall of the plastic box facing the back of the desiccant wheel using a pen knife.
x) Push 4 pipes through the holes in the plastic box and the back of the square tin box. Make sure the pipes do not touch the round tin box. Secure the pipes by taping them the the plastic box and the metal box using duct tape.
3) Building the sensor system:
a) Connect a relay to the desiccant wheel, fan and hair dryer each. Afterwhich, the three items are to be connected to the Arduino using the relay.
b) Connect the arduino-based hygrometer to the same Arduino.
c) Code the Arduino so that it fits all the requirements such that the dehumidifier works automatically.
4) Putting together the entire set-up:
a) Place the entire set-up in a wooden box along with a hygrometer that faces the front. Paste cling wrap on the opening of the wooden box to make sure it is airtight. Cut two holes in the cling wrap and lead the two pipes that blow out hot air from the hair dryer to the outside of the box.
b) Record the humidity level shown on the hygrometer every 15 minutes. Write the results down in a table. Compare the humidity level in the box with the normal humidity levels. If the relative humidity in the wooden box is lesser than the latter, the experiment is a success.
Risk and Safety
Figure 15 - Risk assessment matrix
- The sharp blades of the fan.
- Likelihood : 1
- Severity : 2
- Risk : 2
- This is highly unlikely to occur as the fan compressor will be inside the whole set up. But, while installing the fan compressor inside the dehumidifier the person might get a small cut or a big one which will hurt them. Hence, it will be best to take precautions while placing the fan compressor inside the dehumidifier. What we can do to prevent this from happening is to protect both sides of the fan with steel protections so nobody will get cut by the fan.
- Hot glue guns
- Likelihood : 2
- Severity : 1
- Risk : 2
- The glue gun will be used often to stick things together and connect objects. Since glue guns are hot, they can be dangerous if not handled with care. Even though they may easily cause harm to us, the potential severity of harm is not high. Therefore, it will not be very risky. Nonetheless, we will still take precautions and not leave the glue gun unattended and look after ourselves.
- Drilling holes into the metal pieces
- Likelihood : 3
- Severity : 2
- Risk : 6
- We have to be cautious while drilling the holes into the metal container as we might drill our hands in the process. In order to safely carry out this process, we went to the factory itself to build out desiccant wheel as they have the right equipments and safety gears. We will wear goggles for protection of the eyes from the debri of the metal from going into our eyes. We will also keep ourselves away from the
- Sawing of wooden pieces
- Likelihood : 3
- Severity : 2
- Risk : 6
- We have to be cautious while sawing the wooden parts. Since the saw may cut our fingers or the wooden parts may scratch us. Therefore, we should be very cautious when sawing. While sawing the wood, we used the metal stand to secure the wood in position to allow it to cut properly. We were also told by the employee on how to saw the wood properly. During the sawing of the wood, we were also told to wear goggles for safety purposes so the dust from the wood will not go into our eyes.
After building the dehumidifier, we will place it in an airtight wooden box, along with a hygrometer. The hygrometer will allow us to observe the change in relative humidity every 15 minutes. The data will then be recorded in a table. The relative humidity of another room will also be observed and recorded down at a 1 hour interval. The relative humidity of the two set-ups will be then compared.
Using the data collected, we will plot a table of the relative humidity of each room at the 15 minute intervals. Afterwhich, we will compare the two results to find out if the relative humidity in the room with the dehumidifier had decreased and by how much. This will allow us to find out if the dehumidifier works in such a way that it fulfills all of its goals. We will also observe whether the dehumidifier is able to switch on and off automatically according to the respective levels of relative humidity.
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