Copyright: Department of Energy Engineering, Technical University of Denmark
Citation: Copyright © Department of Energy Engineering, Technical University of Denmark


About

Refrigeration Utilities

See Help-About menu for version number.

Copyright ©	Department of Energy Engineering

Energy Systems Group

Refrigeration

Technical University of Denmark

Programmed by:

Morten Juel Skovrup

Additional code supplied by:

H.J.H. Knudsen

H.V. Holm

Comments and suggestions for improvement of the program are very welcome !!

Thanks to the following persons for ideas, comments and testing the program:

Alexander Cohr Pachai

Bjarne D. Rasmussen

Arne Jakobsen

Per O. Danig

We are keeping a list of persons who will automatically be e-mailed about new versions. If you want to join this list, send an e-mail to Morten Skovrup ms@et.dtu.dk or Bjarne Rasmussen bdr@et.dtu.dk.

Address:	Technical University of Denmark

Department of Energy Engineering

Att. Morten Juel Skovrup

Building 402

2800 Lyngby

Denmark

e-mail:	ms@et.dtu.dk

This program is freeware. You may freely copy and use it without any charge. This program must not be sold for profit.

Disclaimer:

THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL Department of Energy Engineering or any person mentioned above BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.


Plots-general

When you work with a plot - whether it is a log(p)-h diagram, a T-s diagram, a h-s diagram or an I-x diagram - some things are the same:

You move around in a plot by using the mouse or the arrow-keys on the keyboard. If you use the keybord you can change the distance moved each time you press an arrow-key by pressing:

<+>	on numeric keyboard to increases the distance

<->	on numeric keyboard to decreases the distance

The distance moved each time you press an arrow-key can also be changed by changing the value of "Cursor increment" in the toolbar.

You can measure the distance between two points by pressing the measure butoon on the toolbar, and thereafter click on the two points you want to measure the distance between. The distance is displayed in a dialog where you can copy the information to the clipboard.

The position of the cursor in a plot is indicated in the statusline in the bottom of the window. The position is displayed as thermodynamic coordinates - not as screen coordinates. The coordinates are generally displayed with "to many" decimals - this said to warn about using the displayed values without proper rounding. When you right-click on one of the values, you can change the number of decimals.

You can record the position of the cursor by clicking on the plot as you move around. The recorded positions can be viewed/printed/copied by selecting the Options-Show log menu.

See also:

Save plot

Save settings

Save image

Page setup

Format plot

Format axis

Draw polyline

Drawing text


Shortcuts

Mouse

Double-click	Format selected text or curve

Double-click under x-axis	Format x-axis

Double-click left of y-axis	Format y-axis

Right-click	Stop drawing polyline

Keyboard

Down, left, up, and right- arrow	Move cursor

<Spacebar>	As pressing the left mouse button

<Enter>	As double click

<Esc>	Stop drawing polyline (as right mouse button)

<+> on Num-pad	Increase step size when moving cursor with arrow-keys

<-> on Num-pad	Decrease step size when moving cursor with arrow-keys

Keyboard - Mouse (or Keyboard-Keyboard)

<Ctrl> + Left button (or Spacebar)	Select curve

<Shift> + Left button (or Spacebar)	Select text

<Ctrl> + <Shift> + Left button + Drag	Move selected text

<Alt> + Right button under x-axis or left of y-axis	Auto max-min coordinates on axis

<Alt> + Left button + Drag	Select new max-min coordinates on axis

Menu commands

<Ctrl>+<S>	Save plot

<Ctrl>+<I>	Save Image

<Ctrl>+<P>	Print

<Ctrl>+<X>	Exit

<Ctrl>+<L>	Select next curve type closest to current cursor position

<Ctrl>+<C>	Copy to clipboard

<Ctrl>+<P>	Preferences

<Shift>+<Ctrl>+L	New log(p)-h diagram

<Shift>+<Ctrl>+T	New T-s diagram

<Shift>+<Ctrl>+H	New h-s diagram

<Shift>+<Ctrl>+S	New saturation table

<Shift>+<Ctrl>+A	New table

<Shift>+<Ctrl>+I	New I-x diagram

<Shift>+<Ctrl>+C	Close window

<F5>	Redraw


Save plot

You can save the plots you draw for later usage. The plots will be saved in files with extension ".plt". These files can not be exported to other programs - they are specific to Refrigeration Utilities.

Shortcut:

<Ctrl> + <S>

Menu:

File - Save Plot

See also:

Saving settings

Saving image


Save settings

If you have spend time creating a specific "look" of a plot, you can save this by choosing the Options - Save plot settings menu.

You save all settings of the plot except the curves on the plot.

Note that you also save the max-min coordinates on the axis, this means that you in general can't use settings created on a log(p)-diagram on a T-s diagram or a h-s diagram.

Menu:

Options - Save plot settings

See also:

Formatting plot

Formatting axis


Save image

If you want to use a log(p)-h diagram, a T-s diagram, a h-s diagram or an I-x diagram in a word processor you can export the diagram by choosing the File - Save Image menu.

Note that the size of the saved image will correspond to the size of the image on the screen. See also Preferences

Shortcut:

<Ctrl> + <I>

Menu:

File - Save Image


Page setup

Before you print a plot, you specify margins etc. in this dialog:

Margins

Specify left, right, top and bottom margins. All values are measured from the border of the paper in mm. The minimum values you can choose depend on your printer

Frame plot

Draws a frame around the plot

Indicate holes

This has no effect when you print the plot - but it is useful when you set the margins (standard holes for A4 paper are indicated on the drawing in the dialog).

Add n to linewidth when printing

Adds n pixels to the width of all lines when you print the plot. This is useful if your printer has problems printing thin lines.

All curves in black

Prints all curves in black. This is useful if your printer has problems printing lines in grayscale.

Menu:

File - Page Setup

Toolbar:


Format plot

The following values can be changed for a plot:

Margins

Set the left, top, right and bottom margins in either pixels or mm. The margins are the distance from the margins you specify in Page setup to the axis.

Draw border

Draws lines to the right and at the top of the plot connecting the axes.

Text background invisible

Draws all labels on curves with invisible background.

Background color

Sets the background color for the plot.

Selected curve color

Sets the color a curve will change to when selected.

Menu:

Format - Plot

See also:

Format axis

Save settings


Format axis

In this dialog you set options for the axis. The dialog is the same whatever axis you want to format.

Note that not all of the values can be edited at all times, and especially that some of the values can't be changed for I-x diagrams at all.

Auto max/min value:

When selected the program will try to select maximum and minimum for the axis automatically.

Maximum value:

The maximum value on the axis.

Minimum value:

The minimum value on the axis.

Linear or Log(base 10):

Whether the axis should be linear or logarithmic. When logarithmic is selected, the maximum and minimum values cannot be negative numbers.

Title:

Sets the title of the axis.

Font:

Sets the font of the title.

Title margin (distance between numbers and title):

Specify the distance between the bottom of the numbers on the axis to the top of the title of the axis.

Distance in mm or pixels:

If distance is specified in mm or pixels.

Apperance:

Axis width, style and color

Major tick spacing:

Distance in data units between two major ticks.

Minor ticks pr Major:

The number of minor ticks pr. major. For example if Major tick spacing is 1 and Minor ticks pr Major is 9 you could have the following sequence on an axis: 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 where the small numbers are for minor ticks.

Lengths in mm or pixels:

Selects if all lengths below are specified in mm or pixels.

Length of Major ticks:

Specify the length of the line between the axis and a number displayed on the axis. Major ticks are normally labeled, whereas minor ticks normally are unlabelled and a bit shorter.

Length of Minor ticks:

Specify the length of the line between the axis and a number displayed on the axis.

Spacing between tick and number:

Specify the distance between tick and the number displayed with the tick.

Fixed, Exponential or Time:

Whether the labels should be displayed with a fixed number decimal, as exponential numbers or as time (for example either 111.3 or 1.113e2).

Label at minor ticks:

If there should be labels at minor ticks.

Label at major ticks:

If there should be labels at major ticks.

Number of decimals:

The number of decimals displayed for a label.

Font:

The font used for the labels.

Grid at major ticks:

If there should be grid lines at major ticks.

Grid at minor ticks:

If there should be grid lines at minor ticks.

Style, width, color :

The format of the gridlines (i.e. width, color, dotted line ...)

Shortcuts:

Doubleclick under X-axis

Doubleclick left of Y-axis

Menus:

Format - X-axis

Format - Y-axis

See also:

Format plot

Save settings


Draw polyline

To draw lines on a plot you begin by selecting the Draw - Polyline menu. You then continue as follows:

•	Go to the point where you want to start the polyline and press the left button (or <Spacebar>).

•	Move to the next point and press the left button (or <Spacebar>) again, etc.

•	You finish the line by pressing the right button (or <Esc>).

Note:

Holding down <Shift> fixes x-coordinate

Holding down <Ctrl> fixes y-coordinate

If you want to draw a polygon, you don't have to connect the line ends yourself. When you have finished drawing the line, you select the curve and then select the Edit - Connect Curve Ends menu. This is usefull if you want to draw freehand cycles in a log(p)-h diagram.

Menus:

Edit - Draw Polyline

Edit - Connect Curve Ends

See also:

Format curve

Saving/loading curves


Format curve

To format a curve (change color, width etc.) you first have to select a curve, a curve type or one of the curve types in the Format menu.

The curves on a plot are divided in groups called curve types. This enables you to format several curves at the same time.

In a log(p)-h diagram, for example, the curve types are:

•	Polylines drawn by you

•	Isentrops in gas area

•	Isoterms in gas area

•	Isochors in gas area

•	Cycles

•	and more

You select a curve or curve type by:

•	Selecting the Edit - Select Curve menu and clicking on the curve you want to format

•	Clicking on the curve you want to format while holding the <Ctrl> button.

•	Press <Ctrl> + <L>

Sometimes it can be difficult to select the curve you want to format just by clicking at it. To avoid this problem you can also select a curve by positioning the cursor near it and press <Ctrl> + <L> until the curve is selected. Pressing <Ctrl> + <L> makes the program run through the different curve types on the plot and only select curves in the curve type investigated. <Ctrl> + <L> is a shortcut to the menuitem Edit - Select Next Curve, but the menu item itself is pretty useless (as the cursor is positioned at the menu when you select it) - you should allways use the shortcut.

When the curve is selected it will change color (see also Format plot).

To format just the curve you have selected you:

•	Select the Format - Curve menu

•	Double-click on the plot.

To format all curves of the same type as the one you have selected you:

•	Select the Format - Selected Curve Type menu.

Then the following dialog appers:

Curve style

Here you set the width, color and style of the line. Note: If you are formatting a curve type (for example all isoterms) you can specify a number to add to the width of all lines with a label. If you want all widths to be equal, set the width to add to labeled lines to 0 .

Line between points

Select if you want to draw a line between the points the curve is made of.

Draw selected curve type

Select if you want to draw lines of the selected type. This option is only available if you are formatting a curve type and not just a single curve.

Symbols

Select if you want to draw symbols at the points the curve is made of.

No label or Only text or Text and value:

Specify if you want no label, a label with only text or a label with text and a number.

Front, Value, Back:

Specify the text in front of the Value and after the Value. For example if Value is 750 you could specify Front to "h= " and Back to " kJ/kg" to form the label: "h= 750 kJ/kg"

Label font:

Specify the font of the label.

Label background invisible:

Draws the label with invisible background.

Label end:

Specify the position of the label relative to the curve:

First: At the beginning of the curve

Middle: In the middle

Last: At the end

Label position:

Specify the position of the label relative to the plot:

Inside: Inside the plot

Outside: Outside the plot

Number format:

If a value is specified you can set the format of the value.

Label orientation:

How the label should appear. This option is only available if the label is placed outside the plot:

Angular: The label will follow the inclination of the curve.

Horizontal: The label will be horizontal.

Vertical: The label will be vertical.

Tick:

Places a tick between plot borders and label. This option is only available if the label is placed outside the plot:

mm or pixels: Length of tick in mm or pixels

Ticklength: Length of tick.

Tickspace: Space between end of tick and label.

Shortcuts:

<Ctrl> + Left Button

<Ctrl> + <L>

Doubleclick

Menus:

Edit - Select Curve

Format - Curve

Format - Selected Curve Type

See also:

Draw polyline


Saving/loading curves

When you have selected a curve then you can save the curve to an ASCII file. This you can use to export curves to for example a curve fitting program.

On the other hand you can also load curves from ASCII files. The ASCII files should be column delimited (preferably with space or semicolon) and can contain any number of columns as you will be prompted to select X and Y column. The data in the files should be in the same unit system as on the plot.

Menus:

File - Load Curve

File - Save Curve


Drawing text

You can draw text anywhere on a plot. You draw the text by selecting the Edit - Draw Text menu and then clicking on plot where you want the text.

This brings up the following dialog:

Text:

The text to display.

Font:

The font to use.

Text background invisible:

Draws the text with invisible background.

Rotation

Rotation of text in degrees from horizontal.

Anchor:

Screen: position text relative to the screen

Coordinates: position text relative to the coordinates

If you place text outside the plot your only option is relative to the screen.

Note: The text is more precisely positioned if you place it relative to coordinates.

Menu:

Edit - Draw Text

See also:

Format text


Format text

To format text you first have to select the text.

You select text by:

•	Selecting the Edit - Select Text menu and clicking on the text you want to format.

•	Clicking on the text you want to format while holding the <Shift> button.

When the text is selected (you will see selection rectangles on the corners of the selected text) you can move it by holding <Ctrl> + <Shift> while dragging the mouse.

If you doubleclick on the plot or select the Format - Text menu, the following dialog appears:

Text:

The text to display.

Font:

The font to use.

Text background invisible:

Draws the text with invisible background.

Rotation

Rotation of text in degrees from horizontal.

Anchor:

Screen: position text relative to the screen

Coordinates: position text relative to the coordinates

If you place text outside the plot your only option is relative to the screen.

Note: The text is more precisely positioned if you place it relative to coordinates.

Shortcuts:

<Shift> + Left Button

<Ctrl> + <Shift> + Left Button + Drag

Doubleclick

Menus:

Edit - Select Text

Format - Text

See also:

Drawing text


Log(p)-h diagram

Drawing a log(p)-h diagram can produce numerical errors - especially around the critical point. The program is designed to account for these errors and still attemt to draw the diagram. Therefore you should allways examine the diagram to look for errors. If you choose the Options - View errors menu, you get a list of the errors the program found. Note though that no error is not a guarantee that the diagram is without errors - this is especially true if you attempt to draw curves in the liquid phase.

When the log(p)-h diagram is drawn, you can draw either freehand cycles or use one of the 4 predefined cycles the program knows.

Before you draw a log(p)-h diagram you have to fill out the following dialog:

Here you select which refrigerant you want to draw a log(p)-h diagram for.

You can if you have RefProp 6 installed, also choose to use RefProp equations (see also Preferences.)

The two next pages in the dialog enables you to customize the log(p)-h diagram. If you want to use default values, you don't have to make any changes - just select the refrigerant and press OK. If you do make changes, you can save/load them by pressing the respective buttons or restoring default values by pressing the Default button. The default values are specific to each refrigerant, but can be changed by changing Preferences.

The settings you can change are:

Pressure unit:

Set the unit on the Y-axis ([bar] or [kPa]).

Max-Min pressure:

Set the maximum and minimum values for the Y-axis.

Entropy step:

Set the distance between enthalpy curves

Temperature:

Max: Set the maximum temperature

Step: Set the distance between the curves you want to draw

Numbering interval: Set the distance between the curves that will be labeled.

Enthalpy:

Step: Set the distance between enthalpy curves

Numbering interval: Set distance between curves that will be labeled.

Zero factor: Set the zero factor (shifts the saturation envelope to the right on the plot).

Number of isochores in every decade:

Set how many isochors you want to draw - examples are shown.

Distance between quality curves:

Sets the distance between the quality curves you want to draw.

Isotherms and Isentrops in liquid phase:

Drawing curves in the liquid phase can cause problems depending on the refrigerant you select. You should be able to see if the curves are invalid.

Only superheated area:

If you select this option, only the superheated area will be drawn.

On this page you can change the reference for entropy and enthalpy. The default value for most refrigerants is IIR-standard (200 kJ/kg and 1 kJ/(kg K) for saturated liquid at 0 °C).

Menu:

File - New - Log(p)-h Diagram

Toolbar:

See also:

Drawing cycles

One stage cycle

Two stage cycle with open intercooler

Two stage cycle with closed intercooler

Two stage cycle with open intercooler and load at intermediate pressure

Preferences


Drawing cycles

The program knows about four cycles:

•	One stage cycle

•	Two stage cycle with open intercooler

•	Two stage cycle with closed intercooler

•	Two stage cycle with open intercooler and load at intermediate pressure

These cycles can be drawn, the program can claculate COP etc. and you can dimension a plant from the data you supply.

Cycles can be copied between log(p)-h diagrams.

You draw on of the four cycles by selecting the Options - Input cycle menu or by pressing the [image] button on the toolbar.

You can also draw other cycles than the four mentioned, but the difference is that the program can't make any calculations on those cycles. You draw your own cycles by:

•	Drawing a polyline (see draw polyline)

•	Select the Options - Input Curve Data menu to input coordinates of the cycle manually.

If you use on of the four cycles you can optain information and do calculations by selecting the Options - Show Cycle Info menu after the cycle is drawn. Doing this the following dialog appears:

The dialog shows the data you have specified for the cycle and you can input one of the following values (it doesn't matter which one you specify - the rest will automatically be calculated):

•	Qe: Load on evaporator.

•	Qc: Condenser heat.

•	m low: Massflow in low stage plant.

•	V low: Volume flow in low stage plant - taken at suction valve.

•	W low: Work of low stage compressor.

•	Q loss low: Heat rejected from low stage compressor.

•	m high: Massflow in high stage plant.

•	V high: Volume flow in high stage plant - taken at suction valve.

•	W high: Work of high stage compressor.

•	Q loss high: Heat rejected from high stage compressor.

These values can only be changed if the cycle isn't specifyed when it was created. This happens if:

•	You create a two stage cycle with open intercooler and load at intermediate pressure - where you have to specify Qe before the program can draw the cycle.

•	If you specify the heat rejected from the compressor as an absolute in [kW]. In this case you again have to specify Qe (or work or massflow) before the cycle can be drawn.

You should also note that you can't change Q loss if it hasn't been implicitly specified (by specifying the temperature after compressor or by specifying Q loss as a percentage of the co pressor work) when the cycle was created.

The values V high and V low are used to calculate the displacement of the low and high stage compressors:

The displacement of the low and high stage compressors is calculated when you input the volumetric efficiencies.

Details about the calculations are given under the specific cycle.

Menus:

Options - Input Cycle

Options - Show Cycle Info

Options - Input Curve Data

Toolbar:

See also:

One stage cycle

Two stage cycle with open intercooler

Two stage cycle with closed intercooler

Two stage cycle with open intercooler and load at intermediate pressure


One stage cycle

For a one stage cycle you have to supply the following data:

In the upper right corner you can select to edit one of the cycles you have allready draw (if any). Clicking the edit button brings up a dialog where you select the cycle you want to edit. If you want to make a copy of the cycle you select the New cycle checkbox.

When you are finished specifying your cycle you can press the Draw cycle button to just draw the cycle on the plot, or you can press the Show info button to go straight to the Cycle info dialog.

Note that you can select the unit for the data you specify. The unit you select has the following meaning dependent on the type of variable you specify:

For temperature:

•	[Bar]: The temperature will be calculated as the saturation temperature corresponding to the specified pressure.

•	[°C]: The temperature will be set to the specified value.

For temperature difference:

•	[K]: The temperature difference will be set to the specified value.

•	[°C]: The difference is calculated as the difference between the specified value and some other temperature (for example will the superheat be calculated as the difference between the specified temperature and the evaporation temperature).

For pressure drop:

•	[Bar]: The pressure drop will be set to the specified value.

•	[K]: The pressure drop will be calculated as a difference between the saturation pressures (for example will the pressure drop through the evaporator be calculated as the difference between the evaporation pressure and the saturation pressure corresponding to the evaporation temperature subtracted the specified value).

Care should be taken when specifying the volumetric efficiency and the heat rejected from the compressor (Q loss). Some confusion has existed about the definition of the isentropic efficiency, but this program uses the ISO-definition:

If the heat rejected from the compressor isn't specifyed as an absolute value, but specified as either a temperature after the compressor or as a fraction of the compressor work, alternative methods are used for calculating the position of point 2.

The resulting cycle will look like this:

And a plant-diagram could look like this:

Menus:

Options - Input Cycle

Options - Show Cycle Info

Toolbar:

See also:

Drawing cycles


Two stage cycle with open intercooler

For a two stage cycle with open intercooler you have to supply the following data:

In the upper right corner you can select to edit one of the cycles you have allready draw (if any). Clicking the edit button brings up a dialog where you select the cycle you want to edit. If you want to make a copy of the cycle you select the New cycle checkbox.

When you are finished specifying your cycle you can press the Draw cycle button to just draw the cycle on the plot, or you can press the Show info button to go straight to the Cycle info dialog.

Note that you can select the unit for the data you specify. The unit you select has the following meaning dependent on the type of variable you specify:

For temperature:

•	[Bar]: The temperature will be calculated as the saturation temperatur corresponding to the specified pressure.

•	[°C]: The temperature will be set to the specified value.

For temperature difference:

•	[K]: The temperature difference will be set to the specified value.

•	[°C]: The difference is calculated as the difference between the specified value and some other temperature (for example will the superheat be calculated as the difference between the specified temperature and the evaporation temperature).

For pressure drop:

•	[Bar]: The pressure drop will be set to the specified value.

•	[K]: The pressure drop will be calculated as a difference between the saturation pressures (for example will the pressure drop through the evaporator be calculated as the difference between the evaporation pressure and the saturation pressure corresponding to the evaporation temperature subtracted the specified value).

Care should be taken when specifying the volumetric efficiencies and the heat rejected from the compressors (Q loss). Some confusion has existed about the definition of the isentropic efficiency, but this program uses the ISO-definition:

If the heat rejected from the compressors isn't specifyed as an absolute value, but specified as either a temperature after the compressor or as a fraction of the compressor work, alternative methods are used for calculating the position of point 2 and 8.

The resulting cycle will look like this:

And a plant-diagram could look like this:

Menus:

Options - Input Cycle

Options - Show Cycle Info

Toolbar:

See also:

Drawing cycles


Two stage cycle with closed intercooler

For a two stage cycle with closed intercooler you have to supply the following data:

All of the values should be self-explaining, but if you're in doubt look at the log(p)-h diagram below.

In the upper right corner you can select to edit one of the cycles you have allready draw (if any). Clicking the edit button brings up a dialog where you select the cycle you want to edit. If you want to make a copy of the cycle you select the New cycle checkbox.

When you are finished specifying your cycle you can press the Draw cycle button to just draw the cycle on the plot, or you can press the Show info button to go straight to the Cycle info dialog.

Note that you can select the unit for the data you specify. The unit you select has the following meaning dependent on the type of variable you specify:

For temperature:

•	[Bar]: The temperature will be calculated as the saturation temperatur corresponding to the specified pressure.

•	[°C]: The temperature will be set to the specified value.

For temperature difference:

•	[K]: The temperature difference will be set to the specified value.

•	[°C]: The difference is calculated as the difference between the specified value and some other temperature (for example will the superheat be calculated as the difference between the specified temperature and the evaporation temperature).

For pressure drop:

•	[Bar]: The pressure drop will be set to the specified value.

•	[K]: The pressure drop will be calculated as a difference between the saturation pressures (for example will the pressure drop through the evaporator be calculated as the difference between the evaporation pressure and the saturation pressure corresponding to the evaporation temperature subtracted the specified value).

Care should be taken when specifying the volumetric efficiencies and the heat rejected from the compressors (Q loss). Some confusion has existed about the definition of the isentropic efficiency, but this program uses the ISO-definition:

If the heat rejected from the compressors isn't specifyed as an absolute value, but specified as either a temperature after the compressor or as a fraction of the compressor work, alternative methods are used for calculating the position of point 2 and 8.

The resulting cycle will look like this:

And a plant-diagram could look like this:

Menus:

Options - Input Cycle

Options - Show Cycle Info

Toolbar:

See also:

Drawing cycles


Two stage cycle with open intercooler and load at intermediate pressure

For a two stage cycle with open intercooler and load at intermediate pressure you have to supply the following data:

All of the values should be self-explaining, but if you're in doubt look at the log(p)-h diagram below. Note though that you have to specify the intermediat load, the load on the evaporator and the intermediate pressure before the cycle can be drawn.

When you are finished specifying your cycle you can press the Draw cycle button to just draw the cycle on the plot, or you can press the Show info button to go straight to the Cycle info dialog.

In the upper right corner you can select to edit one of the cycles you have allready draw (if any). Clicking the edit button brings up a dialog where you select the cycle you want to edit. If you want to make a copy of the cycle you select the New cycle checkbox.

Note that you can select the unit for the data you specify. The unit you select has the following meaning dependent on the type of variable you specify:

For temperature:

•	[Bar]: The temperature will be calculated as the saturation temperatur corresponding to the specified pressure.

•	[°C]: The temperature will be set to the specified value.

For temperature difference:

•	[K]: The temperature difference will be set to the specified value.

•	[°C]: The difference is calculated as the difference between the specified value and some other temperature (for example will the superheat be calculated as the difference between the specified temperature and the evaporation temperature).

For pressure drop:

•	[Bar]: The pressure drop will be set to the specified value.

•	[K]: The pressure drop will be calculated as a difference between the saturation pressures (for example will the pressure drop through the evaporator be calculated as the difference between the evaporation pressure and the saturation pressure corresponding to the evaporation temperature subtracted the specified value).

Care should be taken when specifying the volumetric efficiencies and the heat rejected from the compressors (Q loss). Some confusion has existed about the definition of the isentropic efficiency, but this program uses the ISO-definition:

If the heat rejected from the compressors isn't specifyed as an absolute value, but specified as either a temperature after the compressor or as a fraction of the compressor work, alternative methods are used for calculating the position of point 2 and 8.

The resulting cycle will look like this:

And a plant-diagram could look like this:

Menus:

Options - Input Cycle

Options - Show Cycle Info

Toolbar:

See also:

Drawing cycles


T-s diagram

The T-s diagram is very similar to the log(p)-h diagram - except that the program doesn't support automatic drawing of cycles.

When you select the File - New - T-s Diagram menu the following dialog appears:

Here you select which refrigerant you want to draw a T-s diagram for. Note that you can't draw T-s diagrams for all the refrigerants you can draw log(p)-h diagrams for.

The two next pages in the dialog enables you to customize the T-s diagram. If you want to use default values, you don't have to make any changes - just select the refrigerant and press OK. If you do make changes, you can save/load them by pressing the respective buttons or restoring default values by pressing the Default button - see also Log(p)-h diagram.

Menu:

File - New - T-s Diagram

Toolbar:

See also:

Preferences


Table of saturation values

The table of saturation values are used to display values off:

•	Pressure

•	Specific volume of liquid

•	Specific volume of gas

•	Enthalpy of liquid

•	Enthalpy of gas

•	Heat of evaporation

•	Entropy of liquid

•	Entropy of gas

taken at saturation for a range of temperatures.

Before the table can be made, you have to specify the refrigerant and the temperature range:

The table can be saved as an column delimited ASCII file or be printed.

Menu:

File - New - Saturation table

Toolbar:


Table of thermodynamic and thermophysical values

This table can be used to create a file with values of a thermodynamic or thermophysical property for a refrigerant as a function of some independent value(s). The purpose of this table is to provide a way to generate a datafile which can be exported to a data-fitting program.

Currently the datafile is compatible with the programs Tablecurve 2D and Tablecurve 3D, but the datafile is in ASCII format so it should be possible to export it to other programs.

As independent variable you can currently select:

•	T [°C/K] , p [bar/kPa]

•	T [°C/K] , v [m^3/kg]

•	T [°C/K] , s [J/(kg K)]

•	p [Bar/kPa] , v [m3/kg]

•	p [Bar/kPa] , s [J/(kg K)]

•	p [Bar/kPa] , h [kJ/kg]

•	v [m3/kg] , s [J/(kg K)]

•	v [m3/kg] , h [kJ/kg]

After you have selected the independent variables, you specify a range over which the variables are varied.

The program the creates the table, and you select the property/properties you want to calculate as a function of the two independent variables.

The ranges you specify in the dialog will not be checked in any way, but if a call to a function fails the value in the table will be displayed as "N/A". This will also happen if the equation for the property you specify isn't implemented for the selected refrigerant.

The lines with "N/A" values can easily be removed by pressing [image] before you save the table.

Menu:

File - New - Table

Toolbar:


I-x diagram

You can draw I-x diagrams for moist air at almost any pressure you want.

Before you draw a I-x diagram the following dialog appears:

In the dialog you can set values to customize your I-x diagram. These values should be self-explaining, but try changing them - if you enter illegal values you will get an error message.

Pressing the "Default" button will select default values.

When you have specified the values you want to use, you can save them to a file by pressing the "Save settings" button. You can load saved settings by pressing the "Load settings" button.

After you have drawn the diagram you can save it to disk for later use, print the plot or export the image to Bitmap or Metafile format.

Menu:

File - New - I-x Diagram

Toolbar:

See also:

Preferences


Preferences

When the program starts or when all windows are closed, you'll find a menu-item in the File menu called Preferences.

Selecting this menu enables you to change some of the default values for the program:

On the first page in the dialog you can input some personal data and select which data will appear on plots and other prints created by the program.

With data as indicated above the logo on a log(p)-h diagram will look like this:

In the following pages in the dialog you can specify default values for log(p)-h, T-s, h-s, I-x diagrams and if you want to use RefProp equations. Especially you can select which curves you by default want to be drawn on the diagrams. All the curves will still be created - they'll just be invisible. If you for example select that by default isoterms in the gas area on log(p)-h diagrams won't be drawn, you can allways make the isoterms visible on a specific log(p)-h diagram by selecting the Format - Gas area - Isoterms menu and check the "Draw selected curve type" -checkbox.

You can also select which font to use by default when drawing a diagram. This can be usefull if you plan to export an image to another program. Before you export the image, try setting the small font to 10 pt, normal to 12, Axis title and labels to 14 and large font to 16. Then draw the diagram and select wysiwyg mode and fit to screen before you export the image.

If you select the Equation set tab you can enable support for RefProp 6 equations. You have to supply a path to the fluids-directory or you can try to let the program find it for you.

In the Appearance tab you can select the kind of toolbar images you prefer.


h-s diagram

The h-s diagram is very similar to the log(p)-h diagram - except that the program doesn't support automatic drawing of cycles.

When you select the File - New - h-s Diagram menu the following dialog appears:

Here you select which refrigerant you want to draw a h-s diagram for. Note that you can't draw h-s diagrams for all the refrigerants you can draw log(p)-h diagrams for.

The two next pages in the dialog enables you to customize the h-s diagram. If you want to use default values, you don't have to make any changes - just select the refrigerant and press OK. If you do make changes, you can save/load them by pressing the respective buttons or restoring default values by pressing the Default button - see also Log(p)-h diagram.

Menu:

File - New - h-s Diagram

Toolbar:

See also:

Preferences


DDE

Refrigeration Utilities can act as a DDE-server.

You connect to the server with:

  Service : RefrigerationUtilities

  Topic : RefrigDDEServer

After you connect you can poke data to Refrigeration Utilities with the following Items:

•	CreateLogPh

•	CreateTs

•	CreateIx

The format of the data you send with the poke is as follows:

CreateLogPh

The data is a null-terminated string as accepted by Windows (in Delphi this is called a PChar)

The string has the following format: 'RNumber,h_1,P_,h_2,P_2,...,h_n,P_n'

where

•	Rnumber is the refrigerant number. For example R407C, R134a, R717...

•	h_1,P_1...h_n,P_n is coordinates of a curve you want to draw in the log(p)-h diagram. You can have 0 points (i.e. the string looks like for example: 'R717')

•	h is enthalpy in [J/kg] and P is pressure in [Pa]

•	Note that the values in the string are seperated by comma's (which means that the decimal seperator in h an P should be a period: '.' and NOT a comma)

CreateTs

The data is a null-terminated string as accepted by Windows (in Delphi this is called a PChar)

The string has the following format: 'RNumber,s_1,T_1,s_2,T_2,...,s_n,T_n'

where

•	Rnumber is the refrigerant number. For example R407C, R134a, R717...

•	s_1,T_1...s_n,T_n is coordinates of a curve you want to draw in the T-s diagram. You can have 0 points (i.e. the string looks like for example: 'R717')

•	s is entropy in [J/(kg K)] and T is temperature in [K]

•	Note that the values in the string are seperated by comma's (which means that the decimal seperator in s an T should be a period: '.' and NOT a comma)

CreateIx

The data is a null-terminated string as accepted by Windows (in Delphi this is called a PChar)

The string has the following format: 'In0,[In1,In2,In3,In4,In5,In6,In7,In8,]x_1,I_1,x_2,I_2,...,x_n,I_n'

where

•	The terms in the square bracket are optional (see later)

•	x_1,I_1...x_n,I_n is coordinates of a curve you want to draw in the T-s diagram. You can have 0 points (i.e. the string looks like for example: '0')

•	x is humidity ration in [kg/kg] and I is enthalpy in [J/kg]

•	Note that the values in the string are seperated by comma's (which means that the decimal seperator in x an I should be a period: '.' and NOT a comma)

As noted the terms in the square bracket are optional, or more precisely they depend on the value of In0.

The parameters In0-In8 controls the scaling of the I-x diagram. Their meaning is the same as in the Init I-x diagram dialog. In general:

If In0 equals zero:

The values In1-In8 should be ommitted, and the I-x diagram is drawn in default scale.

If In0 doesn't equal zero, all values In0-In8 has to be specified:

The values In0-In8 has the following meaning:

In0 is pressure in [Pa] (default 1.01325*1e5)

In1 is min. temperature on saturation curve in [K] (default 273.15)

In2 is max. temperature on saturation curve in [K] (default 293.15)

In3 is value of isotherm through upper right corner in [K] (default 298.15)

In4 is inclination of isenthalps in [J/kg] (default 2500*1e3)

In5 is max. number of isenthalps (default 40)

In6 is max. number of isotherms  (default 50)

In7 is max. number of x-lines  (default 20)

In8 is distance between RH-curves (default 0.1)

Note that In0 has a meaning if it's different from zero.