Analysis Of Hydro Fluoro Carbons To Reduce Ozone Depletion

Analysis Of Hydro Fluoro Carbons To Reduce Ozone Depletion

Prof (Dr) P. Mallikarjuna Reddy 1 G. Md .Javeed Basha 2 1(Mechanical engineering, St.Johns College of Engineering and Technology, India)

2(Mechanical engineering, St.Johns College of Engineering and Technology, India)

ABSTRACT: Ozone depletion is one of greatest disasters today. It is familiar to most of us that Hydro Chloro Fluoro Carbons (HCFC) is main reason. Air conditioners are the sources of HCFC. Refrigerants known as CFC12 (R12) and HCFC22 (R22) are stable, remain in the atmosphere for many years, and eventually diffuse into the stratosphere. In the upper atmosphere the refrigerant molecules breakdown and release chlorine, which destroys the ozone layer. In the lower atmosphere the molecules absorb infrared radiation and contribute to global warming. Each chlorine atom released can destroy up to 100,000 ozone molecules before it is removed from the stratosphere. Objective of this project is to present Air conditioners which dont use chlorine; they just release Hydro Fluoro Carbons (HFCs) instead of Hydro Chloro Fluoro Carbons (HCFCs).There are different types of refrigerants used in refrigeration and air-conditioning plants. The refrigerant R-22 which is extensively used in air conditioners belongs to HCFC group, which is to be phased out by 2040. These refrigerants are responsible for Ozone Depletion to a greater extent. It includes chlorine which is the main reason for the depletion of Ozone layer, it is found R 407C is best when compare to that, as this avoids chlorine. Therefore in this paper an analysis has been done on R407c and it is concluded that R407c is an Eco friendly refrigerant to avoid depletion of ozone layer for different applications.

Keywords: Air conditioning, Hydro fluoro carbons, Ozone layer, Refrigerants, Refprop software,

1. INTRODUCTION:

   1. AIR CONDITIONING:

      Air conditioning is the removal of heat from indoor air for thermal comfort. In another sense, the term can refer to any form of cooling, heating, ventilation, or disinfection that modifies the condition of air. An air conditioner (often referred to as AC or air con.) is an appliance, system , or machine designed to change the air temperature and humidity within an area (used for cooling as well as heating depending on the air properties at a given time), typically using a refrigeration cycle but sometimes using evaporation, commonly for comfort cooling in buildings.

   2. Air-conditioning applications:

      Air-conditioning engineers broadly divide air-conditioning applications into what they call comfort and process applications. Comfort applications aim to provide a building

      indoor environment that remains relatively constant despite changes in external weather conditions or in internal heat loads. Air conditioning makes deep plan buildings feasible, for otherwise they would have to be built narrower or with light wells so that inner spaces received sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller, since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.

2. LITERATURE SURVEY:

   Let's take a trip back in time about 3,000 years ago. Of course we'll have to get rid of our cell phones, I-Pods and computers; these cool toys won't do us any good here. The top responses would be "electricity", "running water" and "transportation". With good reason, these answers top the list in most cases but there is one that seems to elude the top of the list and gets little respect for its' impact on the world we live in…Refrigeration. There is no doubt that many inventions have had an impact on our lives but refrigeration and the ability to control our environment has had a much deeper impact than we give it credit for. From ancient food storage techniques to the modern day central air conditioning system, the following will provide you a whole new appreciation for the science and importance of refrigeration.

   1. The Origin of Mechanical Refrigeration:

      Mechanical refrigeration was discovered much by accident. In the late 1800's, coal mines in England were pumping fresh air into the deep shafts of the mines using steam driven compressors. After running these compressors for a long period of time, ice would begin to form on the nozzles of the hoses that carried the air. Here is where the possibilities became endless.

      Again sparing the in depth science involved, this is where it was discovered that the temperature, more specifically the boiling points, of certain liquids and gasses could be manipulated by changing the pressure under which they are kept. Now aside from using a fan to blow air over a bucket of ice, this became the science behind mechanical refrigeration and how we could produce it without the direct involvement of ice.

      Fig no. 2.1.The window air conditioner. Many of which end up here because of improper storage and maintenance.

      Fig no.2.2 The condenser in a central air system.

      Fig no.2.3 A stack of roof top units for mid-sized commercial buildings.

3. REFRIGERANTS:

   The thermodynamic efficiency of a refrigeration system depends mainly on its operating temperatures. However,

   important practical issues such as the system design, size, initial and operating costs, safety, reliability, and serviceability etc. depend very much on the type of refrigerant selected for a given application. Due to several environmental issues such as ozone layer depletion and global warming and their relation to the various refrigerants used, the selection of suitable refrigerant has become one of the most important issues in recent times. Replacement of an existing refrigerant by a completely new refrigerant, for whatever reason, is an expensive proposition as it may call for several changes in the design and manufacturing of refrigeration systems. Hence it is very important to understand the issues related to the selection and use of refrigerants. In principle, any fluid can be used as a refrigerant. Air used in an air cycle refrigeration system can also be considered as a refrigerant. However, in this lecture the attention is mainly focused on those fluids that can be used as refrigerants in vapour compression refrigeration systems only.

   1. IMPORTANCE OF OZONE LAYER:

      Ozone present in the stratosphere forms a protective layer and known as ozone layer, ozonosphere or ozone umbrella…… Its concentration in atmosphere is about 10 ppm. In the upper atmosphere, atmospheric gases absorb the sun's radiation, get ionized, and release molecules. In lower atmosphere, atmospheric oxygen gets dissociated and subsequently combines with molecular oxygen of the upper stratosphere, there by producing ozone.

      O2—– (UVradiation) —->O+O

      O2 + O ———--> O3

      The presence of ozone layer in the stratosphere is of vital significance for all biota, as it absorbs the harmful ultraviolet radiations which are lethal to life……

      O3 + UV radiations——--> O2 + O

      The ozone absorbs ultraviolet radiation and prevent them to reach earth's surface. If these radiations are allowed to reach the earth's atmosphere they will increase the temperature of lower atmosphere to such an extent, that it will be impossible for any life to survive on earth. These UV radiations can cause severe radiation damage in human and animals such as DNA mutation and skin cancer.

4. REF-PROP SOFTWARE:

   ol>

5. Objectives and Scope of the Database:

   REFPROP is an acronym for REFerence fluid PROPerties. This program, developed by the National Institute of Standards and Technology (NIST), calculates the thermodynamic and transport properties of industrially important fluids and their mixtures. These properties can be displayed in tables and plots through the graphical user interface; they are also accessible through spreadsheets or user-written applications accessing the REFPROP DLL or the FORTRAN property subroutines.REFPROP is based on the

   most accurate pure fluid and mixture models currently available.

Table no 5.4 Saturation Table of R 407C at Constant Temperature

1. Iso-property Table Calculation for R 22 and R 407C:

   1. Specify Iso-property Table of R 22 at Constant Temperature:

      By keeping temperature as constant and varying the pressure, the specific iso-property of R 22 is obtain as shown.

      Fig no 5.11 Iso-property Table Information of R 22 at Constant Temperature

   2. Iso-property Table Information of R 22 at Constant Temperature:

      Initial pressure is 110KPa and final pressure is 770kPa by increment of 110KPa as shown in figure 5.10

      Fig no 5.12 Iso-property Table Information of R 22 at Constant Temperature

   3. Iso-property Table of R 22 at Constant Temperature: These are the iso-properties of R 22 at T=280K

      Table no 5.5 Iso-property Table of R 22 at Constant Temperature

   4. Specify Iso-property Table of R 22 at Constant Pressure:

      By keeping pressure as constant and varying the temperature, the specific iso-property of R 22 is obtain as shown.

      Fig no 5.13 Iso-property Table Information of R 22 at Constant Pressure

   5. Iso-property Table Information of R 22 at Constant Pressure:

      Initial temperature is 220K and final temperature is 340K with an increment of 20K as shown.

      Fig no 5.14 Iso-property Table Information of R 22 at Constant Pressure

   6. Iso-property Table of R 22 at Constant Pressure: These are the iso-properties of R 22 at constant P=100kPa

      Table no 5.6 Iso-property Table of R 22 at Constant Pressure

   7. Specify Iso-property Table of R 407C at Constant Temperature:

      By keeping temperature as constant and varying the pressure, the specific iso-property of R 407C is obtain as shown.

      Fig no 5.15 Iso-property Table Information of R 407C at Constant Temperature

   8. Iso-property Table Information of R 407C at Constant Temperature:

      Initial pressure is 110KPa and final pressure is 770kPa by increment of 110KPa as shown in figure 5.10

      Fig no 5.16 Iso-property Table Information of R 407C at Constant Temperature

   9. Iso-property Table of R 407C at Constant Temperature: These are the iso-properties of R 407C at T=280K

      Table no 5.7 Iso-property Table of R 407C at Constant Temperature

   10. Specify Iso-property Table of R 407C at Constant Pressure:

       By keeping pressure as constant and varying the temperature, the specific iso-property of R 407C is obtain as shown.

       Fig no 5.17 Iso-property Table Information of R 407C at Constant Pressure

   11. Iso-property Table Information of R 407C at Constant Pressure:

       Initial temperature is 220K and final temperature is 340K with an increment of 20K as shown.

       Fig no 5.18 Iso-property Table Information of R 407C at Constant Pressure

   12. Iso-property Table of R 407C at Constant Pressure: These are the iso-properties of R 407C at constant P=100kPa

Table no 5.8 Iso-property Table of R 407C at Constant Pressure

1. Plot diagrams for R-22 andR 407C:

   1. T-s Plot diagram for R 22:

      T-s diagram of R 22 as shown in figure.

      Fig.5.15 T-s diagram of R 22

   2. P-h Plot diagram for R 22:

      P-h diagram of R 22 as shown in figure 5.24

      Fig no 5.16 P-h diagram of R 22

   3. P-h Plot diagram for R-22(Includes lines of Constant Entropy):

      P-h diagram of R 22 with constant entropy lines as shown in figure.

      Fig no 5.17 P-h Diagram of R 407C with Constant Entropy Lines

   4. T-s diagram of R 407C :

      T-s diagram of R 407C as shown in figure.

      Fig.5.18 T-s diagram of R 407C

   5. P-h Plot diagram for R 407 C:

      P-h diagram of R 407C as shown in figure.

      Fig.5.19 P-h diagram of R 407C

      5.6.6. P-h Plot diagram for R-407C (Includes lines of Constant Entropy):

      P-h diagram of R 407C with constant entropy lines as shown.

      Fig no 5.20 P-h Diagram of R 407C with Constant Entropy Lines

2. Comparison between R 22 and R 407C:

   1. Comparison graph between R 22 and R 407C at constant temperature 280 K when varying pressure and enthalpy as shown below.

      PRESSURE (kPa)	ENTHALPY (kJ/ kg)
      	R 22	R 407C
      110	417.3	423.2
      220	415.4	420.9
      330	413.4	418.4
      440	411.3	415.8
      550	409	413

      At constant temperature 280K and when varying pressure and enthalpy as shown below.

      This graph depicts the comparison between R22 and R407C. At constant temperature 280K for R22 when pressure increases and the enthalpy decreases. For R407C , this behaviour is similar but the values of enthalpy are high for the same pressure used in R22. This concludes that behaviour of R407C is better when comparing to R22.

   2. Comparison graph between R 22 and R 407C at constant pressure 100kPa and when varying temperature and entropy as shown below.

At constant pressure 100kPa and when varying temperature and entropy as shown below.

This graph depicts the comparison between R22 and R407C. At constant pressure 100kPa for R22 when temperature increases and the entropy increases. For R407C, this behaviour is similar but the values of enthalpy are high for the same temperature used in R22. This concludes that behaviour of R407C is better when comparing to R22.

CONCLUSION:

The comparison between R22 and R407C has been done in two ways. Entropy is placed against temperature and enthalpy is placed against pressure. In both the situations the behaviour is similar but for R407C, the enthalpy or entropy values are high for the same temperature and pressure used in R22. This shows that behaviour of R407C is better when comparing to R22. Chlorine, which is main cause for Ozone layer depletion is being released by R22 refrigerant series air conditioners as a part of HCFC. R407C series is remedy to avoid chlorine and found R407C is best when compared to R 22.

As per the proposed work the refrigerant R407c is considered and analyzed in detail. This is done by the help on NIST software named REFPROP; the various ranges of analysis are Temperature From 220K To 340K, Pressure From 100kPa to 770kPa.

The complete analysis is carried out in S.I. units and the resultant graphs shows that the refrigerant is suitable for using in Refrigeration and Air Conditioning systems.

It may be noted that one chlorine atom can destroy 100000 ozone molecules. The relative ability of a substance to deplete the ozone layer is called ozone depletion potential (ODP).

The CFC refrigerants such as R-11 and R-12 have the highest ODP=1.The HCFC refrigerants have a relatively low ODP, i.e.R-22 has ODP=0.05.The HFC refrigerants do not cause any ozone depletion, i.e.R-134a and R407c has ODP=0.

Therefore in this paper an analysis has been done on R407c and it is concluded that R407c is an Eco friendly refrigerant to avoid depletion of ozone layer for different applications

REFERENCES

1. Rani Tusha and P. Balachander, 2008. Numerical Simulation Of fin and tube condenser in a R22 system charged With R407C, J. Scientific and Industrial Res., 67: 209-218.

2. McLinden MO, Klein SA, Lemmon EW, Peskin AP. NIST thermodynamic and transport properties of refrigerants and refrigerant mixtures (REFPROP), Version 6.0..Gaithersburg, MD: National Institute of Standards and Technology, 1998.

3. Chang SD, Ro ST. Pressure drop of pure HFC refrigerants and their mixtures flowing in capillary tubes. Int J Multiphase Flow 1996;22(3):551 61.

4. Manual as energy Efficiency at design stage, CII Godrej Energy Management Cell-1998 edition

5. CII-Godrej Green Business Centre HVAC 0 &M Manual

6. Adnan Sozen, Erol Arcakliog lu, Tayfun Menli_k and Mehmet Ozalp, 2008. Determination of thermodynamic properties of an alternative refrigerant (R407c) using artificial neural network, Expert Systems with Applications.

7. Kim YC, Cho IY, Choi JM. Experimentation and modeling on the flow of R407C and R290 through capillary tubes. Korean Journal of Air-Conditioning and Refrigeration Engineering 1999;11(4):4928.