Tuesday, February 23, 2010

Guest Lecture 01- Ultraviolet Germicidal Irradiation

The Ultraviolet germicidal irradiation (UVGI) is a method to sterilize which uses ultraviolet light at suitably short wavelength to fracture the microorganisms. It is mostly used in a different range of purpose like cooking, water purification and air. UV is a famous method since 120 years ago. But the fact is UVGI is dangerous to use and it can damage the structure of the existence in the micro organic level. For example using the UVGI machine in some location like circulating air or water systems makes a poisonous effect on micro-organisms.

Indoor microorganisms are in two different categories. First, Pathogens or more commonly germ which is a biological mediator that causes illness to its mass. It includes bacteria and virus. In fact, our body develops numerous natural orders of defense against some of the common pathogens but cannot cover all of them. Pathogenic viruses cause different types of illness like chickenpox, measles, smallpox and rubella. The range of the virus is between 20-300 nanometers in length and it is really small compare to the range of bacteria which is between 1-5 micrometers in length. Second category is Fungi which is includes a eukaryotic territory of microbes that are generally saprophytes but mostly can develop infection in people, animals and plants. Fungi are usually making a yeast infection in the body like in skin and nail. It is usually grow in presence of food like organic material and water. In HVAC system mostly found in cooling coil and damp filter media.

The big discussion in indoor microorganisms is how to control it. As we know HVAC system (Heating, ventilation and air-conditioning) can participate in distribution and control of transmittable microorganisms. For example, for Pathogens the best way to control is remove it from air, remove from surface and limit person to person transmittal with geo hygiene. In addition, for fungi the best answer is control the surface moisture. HVAC ducts are treating as a pipe in the building and the transmittable microorganisms can travel room to room when people socialize in the room, for instance when they talk, laugh, cough and sneeze. It is important because it can be suspended in the air for several hours.

Ultraviolet germicidal irradiation (UVGI) is a good option with high efficiency filtration system to organize the airborne microorganisms. UVGI system is typically low pressure mercury vapor lamps which use 254 nm UVC radiations produced to interrupt the DNA or RNA of microbes and cause impairing their capability of replication. The microbial response to UVGI is as this formula: S=exp(-KIT). S is the survival fraction of a microbial population. Factor K (cm2/μW-s) is represents the resistance of the species of interest. I germicidal radiation at a flounce rate (W/cm2) and T is the time on the formula. Remember that Air temperature and velocity may vary over a wide range in an HVAC system and make considerable change in, Also I and t factor which are infrequently measure for a design and analyses in an accurate way.

One of the good examples of the system type for UVGI is UV above occupied. It is a zone irradiance circulation air. Which the first cost was $2.5 ft2 and operation cost was $0.13 ft2/ year. More models are self contained, decontamination and coil filter bank disinfection.

Small Is Beautiful

Small Is Beautiful (a study of Economics As If People Mattered) written by economist from England whose name is E. F. Schumacher. The expression of the name of the book was basically in contrast with phrases bigger is better which is more popular between people. Since human is small (in size) comparing to its environment can we claim that small is more beautiful?

Basically this essay is divided into different divisions including the modern world, resources, the third world and organization and ownership. On the Problem of Production which we were studying he disagrees with the idea of the sustainable modern economy. He argues that in our modern world natural resources are used as replaceable material which is totally wrong and they are not renewable and should get more attention from government and community. Also we should consider the pollution, environmental issues and ecology problems in our surrounding. Essentially he argues about the responsibility of government who expected to be concerned about sustainable development. The government is not only accountable in developed county but in the third world countries as well. On the second part which is Peace and Permanence (chapter two) writer declare a relationship between war and richness. Our historical evidence shows that the rich people usually more peaceful compare to poor people. Basically they don’t need to fight and gain anything since they are rich enough. But is it an only reason to fight? Or culture and environment are involved as well? In my personal idea it is not the only reason and most of the war started base on lack of education more than money. In part of the essay he claimed that we have science and technology to help us along the road to peace and I believe most of the problem for gaining the peace started from here. In fact, wisdom demands a new direction of science and technology to get the right way to the organic, non-violent and beautiful life.

In the part of role of economics the question is how much we should consider economist. Are they trying to draw a future as a despondent view? Who is economic and how much they know about the economic future? Are they making an exaggeration about our life? If they start to talk about the problems on the future they need to have a solution for it. Some of the fact is, it is not really exaggeration in our situation like natural resources, public disease and population growth. We all know they are in the dangers point and no disagree about the face but how much time we have to get to that miserable point.

Other subject is about the Buddhist Economist which basically means right “livelihood”. It is clear that Buddhist economist have to be extremely different from the economics of modern world. The Buddhist sees the spirit of civilization in the strength of the human character not in a development and production. Character of the human is essentially formed primarily by a man's work. And work, properly conducted in conditions of human dignity and freedom, blesses those who do it and equally their products.

Monday, February 15, 2010

Abstract

An experiment was conducted to test the accuracy of visual observations and analog inclinometer readings. A solar angle calculator was constructed by inputting the trigonometric solar equations into Excel to act as the control to which readings were compared. Data for measurement of solar angles collected from a morning and afternoon of the same day, showed a reasonable level of accuracy with nearly all data falling within a range of 5-15 percent error. The level of error was attributed mostly to user error and the level of graduation of the instrumentation.


Table of Contents

S.No

Description

Page Number

Abstract

02

1.0

Introduction

04

2.0

Experimental Design and Instrumentation

04

3.0

Experimental Procedure

05

4.0

Theory

06

5.0

Analysis: Data Validation/ Analysis & Error Analysis

08

6.0

Conclusion

09

7.0

References

10


1.0 Introduction:

Using two separate measurement methods [visual observation, inclinometer with magnetic compass] the solar altitude and azimuth were calculated for Phoenix both in the morning and evening. Error analysis was then done by comparing the manual measurements with the calculated angles for altitude and azimuth at those times. Finally, the Excel spread sheet prepared for calculations was used to determine the hours of sunrise and sunset for that day.

2.0 Experimental Design and Instrumentation:

The two instruments used for conducting the experiment were the Magnetic Compass and the Inclinometer. The basic working principle and functioning of the two is as follows:

Magnetic Compass: A compass is a navigational instrument for determining direction relative to the Earth's magnetic poles. It consists of a magnetized pointer (usually marked on the North end) free to align itself with Earth's magnetic field. The magnet is generally called a needle. One end of the needle is often marked "N," for north, or colored in some way to indicate that it points toward north.

A compass works by detecting and orienting itself in a magnetic field. Since the Earth is magnetized, on its surface exists a very weak magnetic field. This magnetic field is a result of the rotational forces of liquid iron in the Earth’s core. Earth can be imagined as a gigantic bar magnet with a North-South orientation that causes other magnetized objects to take on the same orientation. However, Earth’s magnetic North is not the same as its geographic North located at the North Pole, but is slightly to one side. This deviation from true North means compensation must be made when calculating actual directions. These compensation factors vary depending on location on the Earth and can be read from navigational charts.

Inclinometer: An inclinometer is an instrument for measuring angles of slope (or tilt), elevation or inclination of an object with respect to gravity by creating an artificial horizon. It is also known as a tilt meter or tilt indicator. Inclinometers measure both inclines (positive slopes, as seen by an observer looking upwards) and declines (negative slopes, as seen by an observer looking downward).

The inclinometer used for the experiment was essentially a radial protractor with a weighted needle in the centre. If the base of the inclinometer is level, its indicating needle or dial points straight up (i.e.90 degrees). The shadow of the needle on the base gives the reading of the altitude angle of the sun. Aligning the shadow on the dial in an accurate manner with the magnetic compass allows us to take the readings for the azimuth angle of the sun. The readings on the magnetic compass are for magnetic north.

Appropriate corrections need to be made for true north in order to get the final result for solar azimuth angle. In case of Tempe, the correction is 12 degrees from magnetic north/south (sign convention used: negative for morning & positive for afternoon or negative when east of south and positive when West of south).

3.0 Experimental Procedure

a. The experiment was conducted for two different times of the same day on February 1st at 10:15 am and 3:00 pm. The solar azimuth and altitude were first estimated using bare eye and the same were recorded.

b. In the next step, the inclinometer was used to record the solar altitude. This device (which consists of a needle in the centre of concentric circles giving the degree measure for altitude angle calculated based on complex solar geometry), was placed in the sun. The length of the shadow of the nail pointed to the solar altitude (measured in degree) on the base.

d. Next, the magnetic compass (aligned to magnetic north) was placed on the base of the inclinometer in such a way that the shadow of the needle now fell on the compass. Since the solar azimuth angle is the measure of the angle between the line from the observer to the sun projected on the ground and the line from the observer due south, the angle between magnetic south on the compass and the line of the shadow was noted.

d. For Phoenix, the correction required to compensate between true and magnetic north is approx 12 degrees. This correction was applied to the reading taken in step c above to get the reading corresponding to true north. By convention, for mornings we subtract 12 degrees and for afternoons add 12 degrees to get values for true north.

e. An excel spreadsheet was prepared to calculate the solar angles using trigonometric solar formulae. The sheet was used to compare and verify the results recorded from above experiment. Spreadsheet data was used as a baseline to analyze the error associated with observations made by bare eyes and experimental tools.

f. The Sunrise and Sunset time for the day was calculated using the spreadsheets generated.

4.0 Theory

The experiment essentially aimed at understanding the solar geometry and developing the skill to measure solar angles using various methods i.e. using formulae, Inclinometer & Magnetic Compass and through visual analysis. The basic theory behind the solar angles measured is as given below.

Solar Geometry: The tilt of the earth on its axis and our location north of the equator result in sun path which changes throughout the year. The position of the Sun with respect to earth’s surface can be described by two different angles, the solar azimuth and the solar altitude or elevation. Together, the two angles provide useful information about the orientation of incoming sunlight on an object or structure. This information is extremely important while installing solar collector devices and designing building fenestrations and shading devices.

Solar Zenith Angle (θs): Angle between a line pointing to the Sun and the vertical. The solar Zenith angle can be calculated using the formula:

Cosθs=Cosλ * Cosδ * Cosω + Sinλ * Sinδ

Where; λ = Latitude; δ = Declination; ω=hour angle

Solar Azimuth Angle (ϕs): The angle between the line from the observer to the sun projected on the ground and the line from the observer due south. A positive azimuth angle generally indicates the sun is east of south, and a negative azimuth angle generally indicates the sun is west of south. Others define solar azimuth as the angle from due north in a clockwise direction as well. The solar Azimuth angle can be calculated as follows:

Sinϕs= (Cosδ*Sinω)/Sinθs

Where; ϕs = Solar Azimuth Angle; δ = Declination; ω=hour angle; θs = Solar Zenith Angle

Solar Altitude Angle (αs): The angle between a line from a point on the Earth's surface to the center of the solar disk, and a line extending horizontally from the point.

αs= 90 – θs

Where; θs= Solar Zenith Angle


5.0 Data Analysis

Location: Tempe, Arizona Date: 01 February 2010

Inputs

Value

Units

Inputs

Value

Units

Solar Time

9.57

Hours

Solar Time

14.32

Hours

Day of Year

32

Day

Day of Year

32

Day

Latitude

33.43

Degrees

Latitude

33.43

Degrees

Longitude

112.02

Degrees

Longitude

112.02

Degrees

Equation of Time

-13

Minutes

Equation of Time

-13

Minutes

Tilt of Surface

0

Degrees

Tilt of Surface

0

Degrees

Surface Azimuth

0

Degrees

Surface Azimuth

0

Degrees

Outputs

Outputs

Declination

-17.37

Degrees

Declination

-17.37

Degrees

Hour Angle

-36.52

Degrees

Hour Angle

34.73

Degrees

Solar Zenith

61.60

Degrees

Solar Zenith

60.65

Degrees

Solar Altitude

28.40

Degrees

Solar Altitude

29.35

Degrees

Standard Time

10.25

Hours

Standard Time

15.00

Hours

Solar Azimuth

-40.22

Degrees

Solar Azimuth

38.59

Degrees

Angle of Incidence

61.60

Degrees

Angle of Incidence

60.65

Degrees

10:15am Standard Time

3:00pm Standard Time

Results

Altitude

Azimuth

Results

Altitude

Azimuth

Visual Estimate

30

-30

Visual Estimate

25

45

5.33%

-34.07%

11.44%

-9.09%

error

Inclinometer

27

-43

Inclinometer

20

44

-5.19%

6.47%

-10.70%

-11.57%

error

Calculation

28.4

-40.22

Calculation

22.14

49.09

Sunrise

6:53 AM

Solar time

7:29 AM

Standard Time

Sunset

5:13 PM

Solar time

5:53 PM

Standard Time

Error Analysis

In addition to a diminished level of accuracy due to imperfection in its making, some level of error can be contributed to the surface which the inclinometer was placed. When placed on a non-level surface the readings of the instrument can be distorted by either the shadow of the nail increasing in length with the instrument tilted away from the sun, or decreased with a tilt toward the sun. Another source of error would be the level of graduation of the inclinometer. With increments of only every ten degrees all measurements which fell between the markings had to be inferred, which carries with it an inherent level of error. The accuracy of the magnetic compass also suffered from its level of graduation as verifying increments proved to be difficult. Both instruments would likely yield a more accurate result with increased scale.

6.0 Conclusions

1. The lab experiment helped in understanding and strengthening the concepts of solar angles. It helped in developing the skill set to use instruments such as the Inclinometer and magnetic compass. The measurements taken using these instruments were cross-checked using the trigonometric equations for solar angles. The two were compared for errors and analysis made to determine possible reasoning for the difference.

2. Data collected from a morning and afternoon reading of the same day, showed a reasonable level of accuracy with nearly all data falling within a range of 5-15 percent error. The level of error was attributed mostly to user error and the level of graduation of the instrumentation.

3. It was concluded that with more accurate and sophisticated instruments, the readings would have been very close to the values obtained using trigonometric functions.


7.0 Reference

1. http://monsterguide.net

2. www.wikipedia.com

3. http://www.teachengineering.org