lab report:Screw Thread Measurement

TITLE:
Screw Thread Measurement.

OBJECTIVE:

1. To measure the Major Diameter, the Minor Diameter and the Effective Diameter of a Screw Plug Gauge using Floating Carriage Diameter Measuring Machine and Horizontal/Vertical Profile Projector.
2. To compare the reading between 2 measuring machine.
3. To compare the reading with the standard value.
4. To evaluate the reading. 

APPARATUS:

1. Floating Carriage Diameter Measuring Machine
2. Set of calibrated screw thread measuring wires (B8)
3. Set of Metric Cylindrical Standards (M24)
4. Vertical Profile Projector
5. Horizontal Profile Projector
6. Set of Core Prisms ( Steel Prisms)

THEORY:

This is a projection apparatus that can produce an enlarge projection shadow of an object. The projection methods of examination methods are well adapted to the examination of form tools, profile gauges, press tools, gear teeth, screw threads, etc. Sizes of the object may be checked by direct measurement on the enlarged shadow and subsequent division by the multiplication factor. The magnification factor is accurate and that the design of the apparatus permits maximum latitude in holding and adjusting the object.

• Major Diameter

The major diameter can be measured with a micrometer, caliper or steel rule. Major diameters are generally the first numbers found in thread designations. A 1/2-10 Acme thread for example, has a major diameter of 500 in. Care must be taken to measure the major diameter on a section of the screw thread that is not worn. A worn portion will measure smaller (or larger if burrs have been rolled up) than the original major diameter. Therefore, it is good practice to measure the major diameter over the least used section of the screw.

• Minor Diameter

The minor diameter can be determined by direct measurement on an optical comparator or by measuring the depth of the thread with a depth micrometer and subtracting twice the measured depth of thread from the major diameter. When using a comparator to measure the minor diameter, remember that the reflected image is reversed (except on modern, image correcting comparators). This means that the bottom of the shaft is shown at the top of the screen. Often oil from the shaft runs down and collects on the bottom of the thread grooves increasing the shadow image. If the oil is not removed, a false (oversized minor diameter) reading will result.

• Effective Diameter 

The pitch diameter is the diameter at which the thread tooth and the thread space are equal. To accurately measure the pitch diameter requires an optical comparator or thread wires. The optical comparator is the easiest to use as the measurement can be directly made and no mathematics are necessary. The disadvantage to the optical method is that the screw must be physically removed from the machine and taken to the comparator. Also, many small shops may not be equipped with a comparator. Measurement over thread wires is an attractive alternative to the comparator for measuring pitch diameter. These measurements can be made directly on the screw. Thread wire measurements are quite accurate, however, they require the use of mathematical formulas along with thread form and pitch information to translate the measurement results into the pitch diameter. The mathematical formula can be found in the Screw Thread Standards for Federal Services Handbook H28 or other engineering handbooks dealing with threads. Roton's application engineers can help you with a library of computer software which does all the complex calculations in seconds. Contact our application engineers for more details and on-line assistance with wire measurements and calculations.

PROCEDURE:
Floating Carriage Diameter Measuring Machine

• Major Diameter

1. The position of the fiducial indicator and the micrometer anvils so that the gauge to be measured is between or within the range of the micrometer
2. A suitable Standard Cylinder was placed between the centres. The suitable Standard Cylinder should have diameter within 1mm of the actual major diameter of workpiece. Time for temperature stabilisation and centralisation of the fiducial indicator was allowed and the reading of the micrometer drum “R1”.
3. The standard was removed and was replaced with the workpiece to be measured. The micrometer drum reading “R2”was been noted.
4. The Major Diameter Dmajor of the workpiece is been evaluated.

• Minor Diameter

1. The position of the fiducial indicator and the micrometer anvils so that the gauge to be measured is between or within the range of the micrometer
2. A suitable Standard Cylinder was placed between the centres. The selected prisms was been inserted between the standard and the anvils. The hanging prisms should be vertical. The reading on the micrometer drum “R3” was been noted.
3. The standard was removed and was replaced with the workpiece. The prisms was been inserted between the thread grooves and the anvils, and the micrometer reading “R4” was noted.
4. The Minor Diameter Dminor of the workpiece is noted.

• Effective Diameter

1. A suitable Standard Cylinder was placed between the centres. The suitable Standard Cylinder should have diameter within 1mm of the actual effective diameter of workpiece.
2. The wires selected were inserted in positions between the Standard Cylinder and micrometer anvils. The wires are selected accordance with N.P.L. recommendation. The reading on the micrometer drum “R3” was noted.
3. The standard cylinder was replaced with the Screw Plug Gauge. Note the micrometer reading “R2” with the wires inserted in the thread grooves.
4. The Effective Diameter Deff of the Screw Plug Gauge was evaluated

Profile Projector

A briefing session will be conducted prior to students carrying out the measurement on the specimen. Please take note of the procedures for setting up the specimen on the adjusting table. Adjust the magnification to ensure the shadow obtained is sharp and clear. Movements can be made through micrometer adjustment. Parameters to be measured on the specimen are:

• major diameter
• minor diameter
• effective diameter

SAMPLE CALCULATION:

• Major diameter

Dmajor = D1 + (R2 – R1)

           = 24 + ( 3.154 – 3.124 )

           = 24.030 mm

• Minor diameter

Dminor = D1 + (R4 – R3)

           = 24 + (8.092 – 12.524)

           = 19.568 mm

• Effective diameter

D3 = D1 + (R6 – R5)

      = 24 + (4.072 – 7.286)

      = 20.786 mm

P = 0.86602(3.0) – 1.820

    = 0.778 mm


Deff = D3 + P

       = 20.786 + 0.778

       = 21.564 mm

• Percentage error

     For Major Diameter of the Floating Carriage Diameter

Percentage error = 24.030 – 24mm x 100%

                                                24

                          = 0.125%

     For Major Diameter of the Profile Projector
Percentage error = 23.992mm – 24mm x 100%
                                                 24 

                          = 0.033%

DISCUSSION:
From this experiment, we have study about to measuring screw thread by using 2 types of machine which are known as floating carriage diameter measuring machine and the profile projector. By using floating carriage measuring machine, we have measured the internal diameter for the screw thread. The major diameter value is 24.030 mm, the minor diameter value is 19.568 mm and the effective diameter value is 20.786mm. The percentage error for major diameter value compare with the standard value is 0.125%.

For the second machine, profile projector that was used to measure the screw thread. In this experiment two types of profile projector vertical and horizontal profile projector. The major diameter value is 23.992 mm and for minor diameter value is 19.875 mm and the effective diameter value is 22.041 mm. The percentage error for major diameter value compare with the standard is 0.033%.

There are many possible errors that can occur during the experiment. The possible errors involved include the miss alignment of the workpiece where the workpiece may not be placed at the correct coordinate or axis. There is no a fix location to place the workpiece and scale to align workpiece. Other possible errors are the position of the student’s eyes during the time the reading is taken may contribute to the error itself. Miss position measured surface may also be the possible error for this experiment. Temperature in the laboratory may also affect the metal size due to thermal contraction. So, measurement may vary.

There are necessary precaution which must be implementing during the experiment is done:

1. The measured surface must first be clean from all contaminant such as oil, dust, moisture and many more. This is to ensure the accurateness of each reading. 
2. The workpiece must be placed at the correct position where the projector can show the image clearly so that we can take the reading correctly.
3. The workpiece must be clamped rigidly so that it is not moveable during the experiment done. Other that to ensure the accuracy of the reading, this measurement is also taken to avoid or minimize error.
4. The person who takes the reading must be in right position to avoid parallax error.

CONCLUSION:
From the experiment, we have learned how to use both Profile Projector and also Floating Carriage Diameter Measuring Machine to measure the profile and the dimensional of the workpiece ourselves. Both machines were successfully used to measure the Major Diameter, the Minor Diameter and the Effective Diameter of a Screw Plug Gauge. After measuring we were able to compare the readings between both measuring machines. The value we obtained was closed to the standard value. In conclusion, all the objectives were achieved successfully therefore the experiment was success.

RECOMMENDATION:
The measured surface must first be clean such as from oil, dust, and moisture. This is to ensure the reading is accurate. The workpiece must be placed at the correct position where the projector can show the image clearly so that we can take the reading correctly. The workpiece must be clamped rigidly so that it is not move during the experiment done. The person who takes the reading must be in right position to avoid parallax error.

REFERENCE:
1. http://www.engineersedge.com/screw_threads_chart.htm
2. http://www.threadcheck.com/the-three-wire-method-of-measuring-pitch-diameter/technicalinfo/
3. http://en.wikipedia.org/wiki/Screw_thread
4. http://www.mfg.mfu.edu/cyberman/quality/metrology/dimension/htm

lab report: sprinkler system

INTRODUCTION

Fire sprinkler system is a system of piping designed in accordance with fire protection engineering standards and installed to control or extinguish fires. A sprinkler system works as the water from a network of overhead pipes is released through nozzles that open automatically with the rise in temperature. The basic components of sprinkler system are the sprinklers, system piping and a dependable water resource. Most systems also require an alarm and system control valves.

Sprinklers may be required to be installed to reduce potential property losses or business interruption. There are two installation systems for the sprinkler which is wet pipe system and dry pipe system. By a wide margin, wet pipe sprinkler systems are installed more often than all other types of fire sprinkler systems. They also are the most reliable, because they are simple, with the only operating components being the automatic sprinklers. When an automatic sprinkler is exposed for a sufficient time to a temperature at or above the temperature rating, the heat sensitive element releases allowing water to flow.

Dry pipe systems are installed in spaces in which the ambient temperature may be cold enough to freeze the water in a wet pipe system, rendering the system inoperable. Dry pipe systems are most often used in unheated buildings, in parking garages, in outside canopies attached to heated buildings. Dry pipe systems are the second most common sprinkler system type.

There are several types of sprinkler head;

1. Quartzoid Bulb Type Head
2. Fusible Soldered Strut Type Head 
3. Duraspeed Soldered Type Head 

Common building used Quartzoid Bulb Type Head with red colour of liquid. For the red colour, the temperature required to shatter the glass is about 68˚C.

OBJECTIVE 

1. To understand how the fire sprinkler systems operate.
2. To recognize a various types of sprinkler head. 

APPARATUS

Fire sprinkler system, stopwatch, lighter, fire starter 

METHODOLOGY

1. Automatic sprinkler head system unit has been prepared.
2. A fire starter was burned by using lighter.
3. Stopwatch was started when finish placed the fire starter.
4. The stopwatch was stopped when the sprinkler head is shattered the glass, the valve was opened and sprayed to the water.

RESULT

TEST	1	2
COLOR OF SPRINKLER	RED (68°C)	RED (68°C)
PRESSURE IN THE PIPE	60 psi	60 psi
TIME	37s	60s

DISCUSSIONS

The experiment that we done show that the time was taken start from the burning of a fire starter on steel net below the sprinkler head until the sprinkler head is shatter the glass. The pressure gauge reading and the pressure in the pipe were setting before the starting of burning.

For the first test, the time is shorter than the second test that is 37 s for the first while the second test is 60 s. The different of the time is because of the fire burning below the sprinkler head for the first test is much larger than the second test.

From this experiment, it shows that the Red color type of sprinkler is suitable used in office building. This is because the minimum heat that will shatter the glass is 68°C. It is not suitable to use in factory building. This is because the heat in the factory is higher than in office building.

Besides that, it shows that the efficiency of liquid in the glass is important to make sure the glass was shattered in the right temperature. When the temperature was achieved its limit, the liquid in the glass will expand and make the glass shattered. So that, the glass will lost its function to stop the water flow from the pipe to let it out and spreading by the sprinkler head to decrease the burning.

CONCLUSION

From the experiment that we have done, we can get know about the types of sprinkler. Actually, the sprinklers have many types and each type have their own characteristic. The color in the sprinkler can be determining the degree celcius of heated. For example, blue color (141°C), green (93°C), red (68°C) and others. We are also know that the sprinkler important to use anywhere for our safety. It is especially for the building like office, hospital, store, factory, school, or others place that involved human safety and things.

The different place have difference sprinkler. It is because; the sprinkler will put in the suitable place. For example, the red color of sprinkler not suitable to put in the factory or cooking place such restaurant. It is because; the degree celcius of heated is minimum 68°C. While, in the factory or restaurants have the higher of heat. So, the suitable colors that can use in those places are blue color. So, for the conclusion we can conclude that the sprinkler will detect the heat using their own colors.

RECOMMENDATION

1. The fire sprinkler system must be checked regularly by scheduled maintenance
2. Every building must install the sprinkler system as their fire fighting system
3. The appropriate colour of liquid must be suitable with the function of the place. 

REFERENCES

1. Building Services and Equipment, Second Edition
2. Building Services ECM 216 Text Book
3. http://en.wikipedia.org/wiki/Fire_sprinkler
4. http://goliath.ecnext.com/coms2/gi_0199-2295132/Review-on-the-design-and.html
5. http://www.articlealley.com/article_249368_27.html
6. http://www.wisegeek.com/what-is-an-automatic-sprinkler-system.htm 

lab report: force convection

OBJECTIVE

To demonstrate the effect and the use of finned surface and pinned surface to improve the heat transfer in forced convection.

INTRODUCTION

Convection is the movement of molecules within fluids (i.e. liquids, gases). It cannot take place in solids, since either bulk current flows or significant diffusion can take place in solids. Convection is one of the major modes of heat transfer and mass transfer.

Forced convection is a mechanism, or type of heat transport in which fluid motion is generated by an external source (like a pump, fan, suction device, etc.). It should be considered as one of the main methods of useful heat transfer as significant amounts of heat energy can be transported very efficiently and this mechanism is found very commonly in everyday life, including central heating, air conditioning, steam turbines and in many other machines. Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream (the case of a shuttle wing during re-entry, for example). However, in any forced convection situation, some amount of natural convection is always present whenever there are g-forces present (i.e., unless the system is in free fall). When the natural convection is not negligible, such flows are typically referred to as mixed convection.

The removal of excessive heat from system components is essential to avoid damaging effects of burning or overheating. Therefore, the enhancement of heat transfer is an important subject of thermal engineering. Extended surfaces (fins) are frequently use in heat exchanging devices for the purpose of improve the heat transfer between a primary surface and the surrounding fluid. Various types of heat exchanger fins ranging from relatively simple shapes, such as rectangular, square, cylindrical, annular, tapered or pin fins, to a combination of different geometries, have been used. The study of improving heat transfer performance is referred to as heat transfer augmentation, enhancement or intensification.

The heat transfer augmentation is very important subject in industrial heat exchangers and other thermal application. Extended surfaces, which are popularly known as fins, are extensively used in air-cooled automobile engines and in air-cooled aircraft engines. Fins are also used for the cooling of computer processors, and other electronic devices. In various applications heat from the fins is dissipated by natural as well as forced convection and radiation. Fins are used as arrays in all the applications.

Thus, our experiment is to demonstrate the use of a fin (extended surface) to improve the heat transfer in forced convection. More about this was explained details in this report.

THEORY

Heat transfer from an object can be improve by increasing the surface area in contact with the air by adding fins or pins normal to the surface. This can be seen in Newton’s Law of Cooling that states that the rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings, which defines the convection heat transfer rate.

The constant of proportionality h is termed the convection heat-transfer coefficient. The heat transfer coefficient h is a function of the fluid flow, so, it is influenced by the surface geometry, the fluid motion in the boundary layer and the fluid properties as well. The effect of the surfaces can be demonstrated by comparing finned and unfinned surfaces with a flat plate under the same conditions of power and flow.

A heated surface dissipates heat to the surrounding fluid primarily through a process called convection. Heat is also dissipated by conduction and radiation, however these effects are not considered in this experiment. Air in contact with the hot surface is heated by the surface and rises due to reduction in density. The heated air is replaced by cooler air, which is in turn heated by the surface, and rises. This process is called free convection.

Convection heat transfer from an object can be improved by increasing the surface area in contact with the air. In practical it may be difficult to increase the size of the body to suit. In these circumstances the surface area in contact with the air may be increased by adding fins or pins normal to the surface. These features are called extended surfaces. A typical example is the use of fins on the cylinder and head on an air-cooled petrol engine. The effect of extended surfaces can be demonstrated by comparing finned and pinned surfaces with a flat under the same conditions of power input and airflow.

Forced convection is a mechanism, or type of heat transport in which fluid motion is generated by an external source (like a pump, fan, and suction device,). It should be considered as one of the main methods of useful heat transfer as significant amounts of heat energy can be transported very efficiently and this mechanism is found very commonly in everyday life, including central heating, air conditioning, steam turbines and in many other machines. Forced convection is often encountered by engineers designing or analyzing heat exchangers, pipe flow, and flow over a plate at a different temperature than the stream. However, in any forced convection situation, some amount of natural convection is always present whenever there are g-forces present (unless the system is in free fall). When the natural convection is not negligible, such flows are typically referred to as mixed convection.

EQUIPMENTS

The surfaces are shown in the figure below. The finned surface consists of 9 fins that are each 0.1 m high and 0.068 m wide. The pinned surface consists of 17 pins that each have a diameter of 0.013 m and are 0.068 m long.

1. Bench top unit with holder
2. Sensors for measuring temperature and flow velocity
3. Air duct
4. "cylinder" heating element
5. Temperature sensor
6. Measuring glands
7. Fan
8. "finned" heating element
9. "flat plate" heating element
10. Display and control unit
11. Handheld sensor to measure airflow velocity

REFERENCES

1. T.D. Eastop, A. McConkey, Applied Thermodynamics For Engineering Technologists 5^th Edition, Pearson Prentice Hall, 1993.
2. Yunus A.Cengel, Heat and Mass Transfer, Third Editions (SI Units) Mc Graw Hill.
3. Yunus A. Cengel, Michael A. Boles, Thermodynamics: An Engineering Approach 5^th Edition, Mc Graw Hill, 2006.
4. www.en.wikipedia.org

lab report: heat exchanger

OBJECTIVE

The main objective for this experiment is to demonstrate the effect of the flow rate variation on the performance characteristics of a counter-flow and parallel flow concentric tube heat exchanger.

Specific objectives for this experiment include:

• Learning how the operation of concentric tube heat exchanger. 
• Developing a set of experiments to obtain statistically significant trends for the overall heat transfer coefficient and the inside heat transfer coefficient as a function of water velocity.
• Observing the difference between parallel-flow and counter flow operation of the heat exchanger.

INTRODUCTION

Heat exchanger is a device built for efficient heat transfer from one medium to another. A solid wall may separate the media, so that they never mix, or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, natural gas processing, and sewage treatment. One common example of a heat exchanger is the radiator in a car, in which the heat source, being a hot engine-cooling fluid, water, transfers heat to air flowing through the radiator (i.e. the heat transfer medium).The main purpose of heat exchanger is to remove the heat from the hot fluid and transfer it into the cold fluid. There are 3 types of heat exchanger, parallel flow, counter flow, and cross flow. However, in this experiment, we only consider the counter-flow heat exchanger and parallel flow. Counter flow exists when the two fluids flow in opposite directions. Each of the fluids enters the heat exchanger at opposite ends. Because the cooler fluid exits the counter flow heat exchanger at the end where the hot fluid enters the heat exchanger, the cooler fluid will approach the inlet temperature of the hot fluid. Parallel flow exists when two fluids flow in parallel directions. Each of the fluids enters the heat exchanger at parallel end.

The variables that affect the performance of a heat exchanger are the fluids’ physical properties, the fluids’ mass flow rates, the inlet temperature of the fluids, the physical properties of the heat exchanger materials, the configuration and area of the heat transfer surfaces, the extent of scale or deposits on the heat transfer surfaces, and the ambient conditions. The comparison between counter-flow and parallel flow also can be determined through this experiment which is explained more in discussion part in this report.

THEORETICAL BACKGROUND

One fluid (hot) convectively transfers heat to the tube wall where conduction takes place across the tube to the opposite wall. The heat is then convectively transferred to the second fluid. Because this process takes place over the entire length of the exchanger, the temperature of the fluids as they flow through the exchanger is not generally constant, but varies over the entire length. The rate of heat transfer varies along the length of the exchanger tubes because its value depends upon the temperature difference between the hot and the cold fluid at the point being viewed.

The way that a heat exchanger works is hot water and cold water entering the exchanger, where the process of cold water gaining some heat and the hot water losing some takes place, before they both exit the exchanger. What is actually happening is, the hot water is heating either the inside or the outside of the tubes in the exchanger, depending on where it is flowing, by what is known as convection.

Then the heat is conducted through the tubes to the other side, either the outside or the inside, where it is then converted back into the cold water raising its temperature. Convection is a mode of heat transfer that involves motion of some fluid that either absorbs heat from a source or gives heat to some surrounding. Conduction is a mode of heat transfer in which the heat is moving through a stationary object or fluid. For a heat exchanger that flows parallel or counter current then the coefficient of heat transfer is called the overall coefficient of heat transfer. It is calculated using the log mean temperature difference, which is found two different ways, depending on whether the flow is parallel or counter.

A heat exchanger is a device by which thermal energy is transferred from one fluid to another. The types of heat exchangers to be tested in this experiment are called single-pass, parallel-flow and counter-flow concentric tube heat exchangers. In a parallel-flow heat exchanger, the working fluids flow in the same direction. In the counter flow exchanger, the fluids flow in parallel but opposite directions.

HISTORY

The primary advantage of a concentric configuration, as opposed to a plate or shell and tube heat exchanger, is the simplicity of their design. As such, the insides of both surfaces are easy to clean and maintain, making it ideal for fluids that cause fouling. Additionally, their robust build means that they can withstand high pressure operations. They also produce turbulent conditions at low flow rates, increasing the heat transfer coefficient, and hence the rate of heat transfer. There are significant disadvantages however, the two most noticeable being their high cost in proportion to heat transfer area; and the impractical lengths required for high heat duties. They also suffer from comparatively high heat losses via their large, outer shells.

The simplest form is composed of straight sections of tubing encased within the outer shell, however alternatives such as corrugated or curved tubing conserve space while maximising heat transfer area per unit volume. They can be arranged in series or in parallel depending on the heating requirements. Typically constructed from stainless steel, spacers are inserted to retain concentricity, while the tubes are sealed with O-rings, packing, or welded depending on the operating pressures.

While both co and counter configurations are possible, the countercurrent method is more common. The preference is to pass the hot fluid through the inner tube to reduce heat losses, while the annulus is reserved for the high viscosity stream to limit the pressure drop. Beyond double stream heat exchangers, designs involving triple (or more) streams are common; alternating between hot and cool streams, thus heating/cooling the product from both sides.

EXPERIMENTAL PROCEDURE

1. This experiment was started by setting the machine for parallel-flow.
2. The hot water inlet temperature was setted 60oC with decade switch.
3. The cold water volumetric flow rate ( ... ) was set to run at a constant 2,000 cm3/min.
4. Initially, the hot water volumetric flow rate ( ... ) was set to 1,000 cm3/min.
5. This step was repeated for the volumetric flow rate of 2,000, 3,000, and 4,000 cm3/min.
6. Six temperature reading was recorded in the result table.
7. Sufficient time (approximately to be 1 to 4 minutes) is allowed, in order to achieve steady conditions.
8. Step 2 to 7 is repeated for counter-flow heat exchanger operation. 

REFERENCE

1. Heat and Mass Transfer (A Practical Approach) – 3rd Edition, Yunus A. Cengel, McGraw Hill (2006) 
2. http://en.wikipedia.org/wiki/Concentric_tube_heat_exchanger
3. http://www.concentrictubeheatexchanger.com/