Fresh water heat exchanger

1.0 Abstraction

1.1 Objective

The aim of this undertaking was to look into what would be the best pick of stuffs to build a Fresh Water Heat Exchanger. The exact inquiry is outlined below:

Materials for a fresh-water heat money changer

Heat money changers, typically, consist of a set of tubings through which one fluid is pumped, immersed in a chamber through which the other fluid flows ; heat base on ballss from one fluid to the other. The stuff of the tube must carry on heat good, have a maximal operating temperature above the operating temperature of the device, non eat in the fluid, and – since the tubings have to be dead set – have equal ductileness.

Material Choice. Typical demands:

  • Maximum service temperature & gt ; 150 C ( 423 K )
  • Elongation & gt ; 20 %
  • Corrosion opposition in fresh H2O: really good
  • As big a thermic conduction as possible.

1.2 Method

Research was carried out into the design of heat money changers and the types of fresh H2O heat money changers presently available utilizing the cyberspace as the chief tool of pick. Assorted paperss that were appropriate to the design of heat money changers were selected and studied.

For the intent of this study we have assumed that Fresh Water will be fluxing on both the shell and tubing sides of the money changer.

2.0 Executive Summary

A heat money changer is a piece of equipment designed so that heat is removed from a hotter watercourse and transferred to a ice chest watercourse doing the latter to heat up.

There are assorted different types of heat money changers available such as:

  • Shell and tubing heat money changer
  • Plate heat money changer
  • Adiabatic wheel heat money changer
  • Plate five heat money changer
  • Fluid heat money changers
  • Waste heat recovery units
  • Dynamic scraped surface heat money changer
  • Phase-change heat money changers
  • The shell and tubing heat money changer is the most common type of heat money changer used in the procedure industry. It consists of a package of tubings which are contained within really big diameter pipe called a shell. The two watercourses are separated by holding one fluid flow inside the tubing and the other flow exterior. Heat is transferred across the tubing from the hot watercourse to the cold watercourse.

    Research into the country of Fresh Water Shell and Tube Heat Exchangers highlighted the chief country of usage to be in marine warming applications. There are 2 chief utilizations for the Fresh Water Heat Exchangers:

  • To incorporate the engine ‘s fresh H2O chilling system with the hot H2O heating system.
  • To heat domestic H2O for usage in the galley and shower.
  • The fresh H2O heat money changer system is used to heat the inside of the boat and heat the domestic H2O by utilizing the engines waste heat.

    A sample set of heat money changer design computations have been outlined in Section 8 of this study, along with the full set of stairss used to find the stuffs to be used to build the heat money changer, utilizing the CES EduPack 2009 package.

    It is our recommendation, after careful design and analysis, that the heat money changer be constructed as follows:

  • Shell: Stainless steel Steel
  • Tube Sheets: Stainless Steel
  • Tubes: Copper
  • Baffles: Stainless Steel

Reasoning for these material choices are outlined in Section 10.

3.0 Declaration

Design of a Fresh Water Heat Exchanger

6.0 Introduction

A heat money changer is a piece of equipment designed so that heat is removed from a hotter watercourse and transferred to a ice chest watercourse doing the latter to heat up.

There are assorted different types of heat money changers available such as:

  • Shell and tubing heat money changer
  • Plate heat money changer
  • Adiabatic wheel heat money changer
  • Plate five heat money changer
  • Fluid heat money changers
  • Waste heat recovery units
  • Dynamic scraped surface heat money changer
  • Phase-change heat money changers

The shell and tubing heat money changer is the most common type of heat money changer used in the procedure industry. It consists of a package of tubings which are contained within really big diameter pipe called a shell. The two watercourses are separated by holding one fluid flow inside the tubing and the other flow exterior. Heat is transferred across the tubing from the hot watercourse to the cold watercourse.

Research into the country of Fresh Water Shell and Tube Heat Exchangers highlighted the chief country of usage to be in marine warming applications. There are 2 chief utilizations for the Fresh Water Heat Exchangers:

  • To incorporate the engine ‘s fresh H2O chilling system with the hot H2O heating system.
  • To heat domestic H2O for usage in the galley and shower.

The fresh H2O heat money changer system is used to heat the inside of the boat and heat the domestic H2O by utilizing the engines waste heat.

This study outlines the stairss involved in the design of a fresh H2O shell and tubing heat money changer. The design carried out in this study was based around fresh H2O fluxing on both the shell and tubing sides of the money changer ( Liquid on the shell side, steam on the tube side ) .

Alterations to both the design computations and the material choice phase bounds, within the CES Software, will be required if alternate fluids are selected.

7.0 What is a Heat Exchanger?

A heat money changer is a piece of equipment designed so that heat is removed from a hotter watercourse and transferred to a ice chest watercourse doing the latter to heat up.

There are assorted different types of heat money changers available such as:

  • Shell and tubing heat money changer
  • Plate heat money changer
  • Adiabatic wheel heat money changer
  • Plate five heat money changer
  • Fluid heat money changers
  • Waste heat recovery units
  • Dynamic scraped surface heat money changer
  • Phase-change heat money changers

For the intent of this study we will be concentrating specifically on the shell and tubing type of heat money changer.

7.1 Shell and Tube Heat Exchanger

The shell and tubing heat money changer is the most common type of heat money changer used in the procedure industry. It consists of a package of tubings which are contained within really big diameter pipe called a shell. The two watercourses are separated by holding one fluid flow inside the tubing and the other flow exterior. Heat is transferred across the tubing from the hot watercourse to the cold watercourse. Again there are assorted different types of shell and tubing heat money changers available, some of which are detailed below:

7.1.1 Concentric Tube Heat Exchanger

This is the most basic type of shell and tubing heat money changer and consists of an interior tubing surrounded by and outer tubing.

Flow if the hot and cold watercourses can be either co-current ( in the same way ) or counter-current ( opposite way ) . This type of heat money changer is frequently used at the lab graduated table or pilot graduated table of the procedure industry. Baffles are sometimes placed in the interior tubing to promote turbulency which in bend increases the inner heat transportation co-efficient ( H ) and therefore the overall transportation coefficient ( U ) and therefore the rate of heat transportation ( Q ) .

7.1.2 Multiple Tube Heat Exchanger

This type of heat money changer consists of multiple inner tubings which are surrounded by and outer tubings. The multiple tubing heat money changers can be individual base on balls or multiple base on balls. In a individual base on balls heat exchanger the fluids will merely flux by each other one time ie: the fluid will flux in one terminal and out the other terminal. In a multiple base on balls heat money changer, in order to increase the surface country for convection relation to the fluid volume, the heat money changer is designed with “ U Tubes ” . The fluid inside the tubes flows in and out at the same terminal of the money changer. This causes the fluid to flux co-current in one part and counter-current in the other. This type of heat money changer is called a 1-2 base on balls heat money changer. This indicates that the shell side fluid passes through the unit merely one time and the tube side passes through the unit twice.

There are many different fluctuations available, such as 1-2, 1-4, 1-6 etc.. and 2-4, 2-6, 2-8 etc… The figure of shell side base on ballss is ever listed foremost.

When planing a heat money changer a different temperature rectification factor is required, depending on the figure of shell and tubing base on ballss in the peculiar unit being designed. The tabular arraies below show the temperature rectification factors to be used.

7.2 Heat Exchanger Components

Heat money changers are the most of import category of heat transportation equipment available in industry because they can be constructed with really big surfaces in a comparatively little volume, they can be fabricated from metal steels to defy corrosion, and they can be used for warming and distilling all sorts of fluids.

A typical heat exchanger consist of the undermentioned points

  • Tubes
  • Shell
  • Baffles and Support Plates for Tubes
  • Tie Rods
  • Tube Sheets/Plate

7.2.1 Tubes

The tubings are normally 19 millimeter or 25 millimeters outside diameter ( do ) . The pitch of the tubings will be dictated by the necessity for cleaning the exterior of the package. If the fluid is likely to do scaling a square pitch is preferred as this permits cleaning round the tubings ; the lower limit spacing is 1.25do between Centres. If infinite is at a premium, or if the fluids are really clean, a triangular pitch is used with a 6 millimeter infinite between the tubings, as this enables well more tubings to be put into a shell.

7.2.1.1. Tube agreements

The tubings in a heat money changer are normally arranged in an equilateral triangular, square, or rotated square form. The triangular and revolved square forms give higher heat-transfer rates, but have a higher force per unit area bead than the square form. A square, or rotated square agreement, is used for to a great extent fouling fluids, where it is necessary to automatically clean the exterior of the tubings. The recommended tubing pitch ( distance between tubing Centres ) is 1.25 times the tubing outside diameter ; and this is what has been used for the intent of the computations in Section 7.

7.2.2 Shells

These are normally made of C steel, and standard pipes are used for the smaller sizes and rolled welded home base for larger sizes ( 0.4-1 m ) . The thickness of the shell can be calculated from the expression for thin-walled cylinders, but a lower limit of 9.5 millimeter is used for shells over 0.33 m outside diameter and 11 millimeter for shells over 0.9 m outside diameter. Unless the money changer works at really high force per unit area, the deliberate thickness will normally be less than these figures, but a corrosion allowance of 3 millimeter is normally added to all C steel parts. There are assorted different shell constellations such as:

  • One Pass Shell
  • Split Flow
  • Divided Flow
  • Two Pass Shell with Longitudinal Baffle
  • Double Split Flow
  • Kettle Type Re-boiler
  • Cross Flow

7.2.3 Baffles and Support Plates for Tubes

As mentioned earlier, these are fitted to increase the rate of flow over the tubing package. The most common type is the segmental baffle with about 25 per centum cut. The diameter is dictated by the tantrum of the package in the shell but should be non more than 5-10 millimeter for bluess, and 2.5-5 millimeter for liquids to let for good work clearance between the baffle and the interior of the shell. Baffles are non usually spaced closer than fifth part of the shell diameter ; really near spacing is avoided because the addition in heat transportation is so little compared with the addition in force per unit area bead. Support plates to keep the tubings in place are similar to the baffles, but the holes for the tubings are merely 0.4 millimeters greater than the tubing diameter, whereas for baffles the clearance may be twice this. These support home bases are fitted at least every 1 m for 19 millimeter tubings and every 60 tubing diameters for larger tubings.

7.2.4 Tie Rods

In order to maintain the tubing package straight, tie rods are fitted to the fixed tubing sheet and to the baffle nearest the drifting tube sheet. Normally between four and six rods of thickness 9.5 – 13 millimeters are necessary. These can be used to keep the baffles and support home bases in place if arms are fitted over the rods between the baffles.

7.2.5 Tube Sheets

To let sufficient thickness to seal the tubings the tube sheet thickness should non be less than the tubing outside diameter, up to about 25 millimeters diameter. The thickness of the tube sheet will cut down the effectual length of the tubing somewhat, and this should be allowed for when ciphering the country available for heat transportation. As a first estimate the length of the tubings can be reduced by 25 millimeters for each tubing sheet.

For a more elaborate computation of tube sheet thickness, the thickness of the fixed tubing sheet is frequently calculated from the expression below:

Where decigram is the diameter of the gasket on the tubing sheet, P the design force per unit area, f the allowable on the job emphasis, and dt the thickness of the sheet measured at the underside of the divider baffle channels. The drifting tube sheet may be made times as midst.

For the intent of this study we will be utilizing the standard 25 millimeter diameter method of ciphering effectual length.

8.0 Heat Exchanger Design Calculations & A ; Material Selection

8.1 Sample Design Calculations

This subdivision outlines the stairss involved in planing a shell and tubing heat money changer.

This heat money changer was designed to wholly change over dry saturated steam to liquid ( Water ) , while maintaining the liquid go outing the money changer at the same temperature as the steam which entered.

Fresh H2O was used as the coolant and I have assumed a counter current flow on the money changer.

The undermentioned values were used in the design:

  • Saturated Steam Flow Rate – 2kg/s
  • Saturated Steam Pressure – 3 Barroom
  • Saturated Steam Temperature ( and liquid temperature ) – 133.5 & A ; deg ; C
  • Fresh Water Temperature ( come ining the money changer ) – 15 & A ; deg ; C
  • Water Flow Rate – 4kg/s
  • Latent Heat of Vaporisation ( ) – 432.8kJ/kg [ Saturated Steam @ 3Bar ]
  • Heat Transfer Co-Efficient ( U ) for Exchanger – 1500W/m2K
  • Specific Heat Capacity of Water – 4.18kJ/kg K

Premise:

No losingss to environment from money changer

8.1.1 Draw a Schematic of the Temperature Profiles:

8.1.4 Calculate Log-mean Temperature Difference:

The chilling H2O has a mass flow rate of 4 kg/s, enters 15 & A ; deg ; C and issues at 66.8 & A ; deg ; C. The log-mean temperature difference has been calculated based upon counter-current flow.

8.1.5 Calculate the surface country and diameter of the money changer:

The overall transportation coefficient, U, for the capacitor was found in Coulson & A ; Richardson Vol. 6, which states that U lies in around 1500 W/m2K. This figure must be assumed so that the maximal surface country of the capacitor can be calculated. The undermentioned expression was used to cipher the surface country of the money changer:

8.1.6 Calculate the figure of tubings in the money changer:

This Effective Heat Transfer Area so has to be divided into tubings within the Heat Exchanger. Standard tubing sizes are an outside diameter ( OD ) of 20 millimeter and an internal diameter ( id ) of 16 millimeter. Tube was taken to be 1.83 m long ( 6 Feet ) , which gives an effectual length of 1.78 m ( Coulson & A ; Richardson et al. , 2004 ) . Calculating the surface country of one tubing can be done utilizing the undermentioned equation:

8.1.7 Calculate package diameter and money changer diameter:

Dividing this by the needed surface country of the capacitor, 57 tubings were needed. This was increased to 60 tubings to add a grade of safety. A 1.25 triangular pitch was employed as the tubing agreement in the capacitor. From this the bundle diameter could be calculated utilizing the undermentioned equation:

Therefore, utilizing a split-ring drifting caput unit, diametral clearance between the shell and tubings of a criterion of 85 millimeter, the shell diameter is 315 millimeter.

8.2 Material Choice

Now that we have calculated the figure of tubings and the diameter of the heat money changer we need to work out the stuff of building for the money changer. As mentioned earlier this money changer has fresh H2O fluxing on both the shell and tubing sides. The design standard states that the stuff of the tube must carry on heat good, have a maximal operating temperature above the operating temperature of the procedure, non eat in fresh H2O, and – since the tubings have to be dead set – have equal ductileness.

Material choice was carried out utilizing the “ CES EduPack 2009 ” stuff choice package and the process is shown in the undermentioned subdivisions.

8.2.1 Material Selection Procedure

8.2.1.1. Limit Phase:

  • Maximum service temperature & gt ; 150 C ( 423 K )
  • Thermal Properties: Set minimal value of maximal service temperature = 150C
  • Elongation & gt ; 20 %
  • Mechanical Properties: Set minimal elongation = 20 %
  • Corrosion opposition in fresh H2O to be really good
  • Lastingness: Water and Aqueous Environments: Tick excellent for lastingness in “ Fresh Water ”

This gives the undermentioned stuffs as consequences:

  • Age Hardening Wrought Al-alloys
  • Brass
  • Bronze
  • Commercially Pure Titanium
  • Copper
  • Nickel
  • Nickel based Super Alloys
  • Nickel Chromium Alloys
  • Non Age Hardening Wrought Al-Alloys
  • Polyetheretherketone ( PEEK )
  • Teflon
  • Silicone Elastomers
  • Stainless Steel

8.2.1.2. Graph Phase

To cut down the list of consequences further, another demand needed to be considered at this point

  • The heat money changer is required to hold every bit big a thermic conduction as possible.

To make this we set up the graph phase with thermic conduction on y-axis and picked the stuffs with the highest thermic conduction.

The graph phase consequences show that the 4 stuffs with the highest thermic conduction are:

  • Copper has a thermic conduction of between 160 – 390 W/m.K
  • Non Age-hardening Wrought Al-Alloys have a thermic conduction of between 119 – 240 W/m.K.
  • Age-hardening Wrought Al-Alloys have a thermic conduction of between 118 – 174 W/m.K.
  • Brass has a thermic conduction of between 100 – 130 W/m.K.

9.0 Market Analysis

9.1 Fresh Water Heat Exchangers

Research into the country of Fresh Water Heat Exchangers has shown that the chief country of usage is in marine warming applications. There are 2 chief utilizations for the Fresh Water Heat Exchangers:

  • To incorporate the engine ‘s fresh H2O chilling system with the hot H2O heating system.
  • To heat domestic H2O for usage in the galley and shower.

The fresh H2O heat money changer system is used to heat the inside of the boat and heat the domestic H2O by utilizing the engines waste heat.

9.2 Existing Systems/Design Requirements

The consequences showed that Copper and Aluminium Alloys were the top two stuffs to build a Fresh Water shell and tubing heat money changer, as they had the highest values for thermic conduction.

9.2.1 Alfa Laval

Alfa Laval, who are the universe leader in heat transportation, centrifugal separation and fluid handling, presently have a Shell and tubing Heat Exchanger for fresh and sea H2O applications for sale which has the undermentioned belongingss:

  • Shell: Carbon Steel
  • Tube Sheets: Carbon Steel
  • Tubes: Integrally Finned Thick Wall Copper Tubing
  • Baffles: Polytetrafluoroethylene

As you can see this matches the consequences that have been obtained from the CES package, Internet Explorer: Copper.

The chief difference between this unit and the unit that has been designed as portion of this study is that R134a refrigerant is used as the chilling liquid as opposed to H2O.

9.2.2 Tubular Exchanger Manufacturers Association, Inc. ( TEMA )

Harmonizing to the TEMA the stuff for the tubings of water-cooled money changers should be selected as follows:

  • If C steel is suited for the procedure fluid ( shell side ) and the H2O is stated as being appropriately treated so that it is non caustic to carbon steel, C steel tubings and tube sheets are acceptable. The usage of C steel tubings for other conditions shall be proposed for understanding by the company.
  • Where the H2O is non specified to be treated as above the undermentioned stuffs shall be used for tubings capable to procedure ( shell ) side acceptableness.
  • Admiralty brass for fresh and recirculated Waterss.
  • Aluminum brass for salt H2O and other caustic H2O.
  • Copper-Nickle tubings for sea H2O.

Again we can see that Brass, Aluminium and Copper are mentioned as suited stuffs for the building of a Fresh Water Heat Exchanger.

10.0 Consequences

It is our recommendation, after careful design and analysis, that the heat money changer be constructed as follows:

  • Shell: Stainless steel Steel
  • Tube Sheets: Stainless Steel
  • Tubes: Copper
  • Baffles: Stainless Steel

10.1 Shell

Stainless Steel been selected for the shell because it meets the demands with respects to service temperature, elongation and corrosion opposition but at the same clip has a lower Thermal Conductivity ( 12 – 24 W/m.K ) .

While we want the shell to possess the same features as the tubing, with respects to service temperature, elongation and corrosion opposition, we do non desire the shell to be as thermally conductive.

This determination has been taken from a safety position. There is no demand for the shell itself to be conductive. If the shell is extremely conductive it could do jobs with scalds and Burnss from people accidently rubbing off the shell. It is safer to utilize a lower thermally conductive stuff.

Stainless Steel is besides an highly lasting and is a clean metal which is used extensively in the procedure industry.

10.2 Tubes

Copper Tubing has been selected for the tubings because it meets the demands with respects to service temperature, elongation and corrosion opposition and has the highest Thermal Conductivity ( 160 – 390 W/m.K ) of all the stuffs.

Besides, as can be seen from the market analysis in Section 9 Cu is presently both, used in and recommended for usage in, fresh H2O heat money changers by the universe leaders in heat transportation, Alfa Laval, and the universe leaders in quality confidence criterions for Shell and Tube Heat Exchangers, TEMA.

The high Thermal Conductivity of Cu makes it an ideal stuff to utilize in the tube in the heat money changer.

While we have selected Cu for the intent of our design, aluminum metals and brass are besides absolutely acceptable stuffs to utilize for the tube in a Fresh Water Heat Exchanger.

  • Non Age-hardening Wrought Al-Alloys have a thermic conduction of between 119 – 240 W/m.K.
  • Age-hardening Wrought Al-Alloys have a thermic conduction of between 118 – 174 W/m.K.
  • Brass has a thermic conduction of between 100 – 130 W/m.K.

10.3 Tube Sheets & A ; Baffles

Stainless Steel will besides be used for the Tube Sheets and Baffles based on its lastingness and its cleanliness.

11.0 Decision

The material choice consequences shown in Section 8 show that Copper and Aluminium Alloys and Brass were the 3 best stuffs to build a the tube for a fresh H2O heat money changer from, as they have the highest values of thermic conduction, while besides run intoing the design standards outlined at the start of this study:

  • Maximum service temperature & gt ; 150 C ( 423 K )
  • Elongation & gt ; 20 %
  • Corrosion opposition in fresh H2O: really good

For the intent of this study we have chosen the undermentioned stuffs for our design:

  • Shell: Stainless steel Steel
  • Tube Sheets: Stainless Steel
  • Tubes: Copper
  • Baffles: Stainless Steel

Brass and Aluminium Alloys are besides absolutely acceptable stuffs which could hold been used in the tubings.

The design carried out in this study was based around fresh H2O fluxing on both the shell and tubing sides of the money changer. Alterations to both the design computations and the material choice phase bounds will be required, if other fluids are required to be used.

12.0 Mentions

  • Coulson & A ; Richardson, ( 1999 ) , Chemical Engineering Design Vol. 1, 3rd Edition
  • Coulson & A ; Richardson, ( 2004 ) , Chemical Engineering Design Vol. 6, 4th Edition
  • Dr. Edmond Byrne, ( 2005 ) , Heat Transfer & A ; Applied Thermodynamics
  • Barry Ronan, ( 2005 ) , Heat Transfer & A ; Applied Thermodynamics, Class Notes ( UCC )
  • TEMA ( Tubular Exchanger Manufacturers Association ) , ( 1994 ) , Engineering and Material Standard for Shell and Tube Heat Exchangers, Original Edition July 1994
  • Alfa Laval, Water cooled capacitors, Shell and tubing capacitors for fresh and sea H2O applications Available at: hypertext transfer protocol: //www.alfalaval.com/solution-finder/products/fresh-water-condenser/Documents/ERC00042EN.pdf [ Accessed on 27th February 2010 ]
  • Shell and Tube Heat Exchanger Available at: hypertext transfer protocol: //en.wikipedia.org/wiki/Shell_and_tube_heat_exchanger [ Accessed on 27th February 2010 ]