apache loads
TRANSCRIPT
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Apache Loads (ASHRAE)
User Guide
IES Virtual Environment
Copyright © 2014 Integrated Environmental Solutions Limited. All rights reserved.
No part of the manual is to be copied or reproduced in any form without the express agreement
of Integrated Environmental Solutions Limited.
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Contents
1 Introduction ........................................................................................................................... 3
2 Analysis type and results file name ....................................................................................... 4
2.1 Analysis type .......................................................................................................................... 42.2 Results file (for both .htg and .clg files) ................................................................................. 5
3 Heating Loads ........................................................................................................................ 6
3.1 Interface for Heating Loads Calculation ................................................................................ 6
3.1.1 Heating Loads Calculation ................................................................................................. 6
3.1.2 Auxiliary ventilation air exchange ..................................................................................... 6
3.1.3 Natural ventilation air exchange ....................................................................................... 7
3.1.4 Include local and (when link ticked opposite) SunCast sky shielding ................................ 7
3.1.5 Include DHW? .................................................................................................................... 7
3.1.6 Time settings for profiles ................................................................................................... 7
3.1.7 Calculate ............................................................................................................................ 7
3.1.8 Save & exit ......................................................................................................................... 7
3.1.9 Close .................................................................................................................................. 7
4 Cooling Loads......................................................................................................................... 8
4.1 Interface for Cooling Loads Calculation ................................................................................. 8
4.1.1 Cooling Loads Calculation .................................................................................................. 8
4.1.2 Auxiliary ventilation air exchange ..................................................................................... 8
4.1.3 Natural ventilation air exchange ....................................................................................... 9
4.1.4 SunCast Link? ..................................................................................................................... 9
4.1.5 Design Day (for profiles) .................................................................................................... 9
4.1.6 Calculation Period.............................................................................................................. 9
4.1.7 Save & exit ......................................................................................................................... 9
4.1.8 Calculate ............................................................................................................................ 9
4.1.9 Cancel ................................................................................................................................ 9
5 Simulation (Heat Balance Method) settings ........................................................................ 10
5.1.1 Simulation Options .......................................................................................................... 10
5.1.2 Output Options ................................................................................................................ 10
5.1.3 Simulation time step........................................................................................................ 10
5.1.4 Preconditioning ............................................................................................................... 10
6 Autosizing settings ............................................................................................................... 11
6.1 Interface for Autosizing settings.......................................................................................... 11
6.1.1 Re-zero autosized parameters ........................................................................................ 11
6.1.2 Undo last autosize ........................................................................................................... 11
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1 Introduction
ASHRAE Loads (also known as Apache Loads or ASHRAE Heat Balance Method) performs
heating and cooling load calculations according to the ASHRAE Heat Balance Method, as
described in the ASHRAE Handbook of Fundamentals.
Results from ASHRAE Loads are displayed by Vista.
For an account of calculation methods used in ASHRAE Loads see ASHRAE Heat Balance
Method Calculation Methods.
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2 Analysis type and results file name
2.1
Analysis type
ASHRAE Loads offers two types of analysis which you can select using the ‘Analysis type’
option. Select ‘Room and Apache system loads’ to perform an analysis of room heating and
cooling loads and the associated loads on Apache Systems.
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Alternatively, select ‘ApacheHVAC system loads’ to analyse loads on a specified ApacheHVAC
system. Then select the ApacheHVAC system using the drop-down menu in the frame headed
‘Simulation (Heat Balance Method) settings’. If you tick the box labelled ‘Update ApacheHVAC
system sizes?’ the equipment sizes calculated by the analysis will be assigned to components in
the ApacheHVAC system.
2.2 Results file (for both .htg and .clg files)
Here you can specify the name given to the two files where the results will be stored. The
Heating Loads and Cooling Loads results are stored in files with extension .htg and .clg,
respectively.
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3 Heating Loads
Heating Loads implements ASHRAE Heat Balance Method procedures for the calculation of
room heating requirements and the sizing of heating equipment.
Steady-state room heat losses are calculated in the absence of casual and solar heat gains. The
calculation optionally includes the effects of mechanical and natural ventilation air exchanges.
The time, day and month of the heating loads calculation can be chosen. Ensure that the time
chosen matches a heated period in the modelled building.
Results are presented (in the program Vista as tables or graphs of room or zone heat loss,
broken down by heat loss mechanism. Losses can be expressed on a floor area or room volume
basis. Room temperatures are also displayed. The data may be exported to other applications
such as spreadsheets and word processors.
For a description of the calculation methods used in ApacheLoads see ASHRAE Heat Balance
Method Calculation Methods.
3.1
Interface for Heating Loads Calculation
3.1.1 Heating Loads Calculation
Tick this box to include a Heating Loads calculation when you click on Calculate.
3.1.2
Auxiliary ventilation air exchange
Air exchanges specified in Room Data are divided into three categories: infiltration, auxiliary
ventilation and natural ventilation. Any infiltration air exchanges are included unconditionally,
but auxiliary and natural ventilation air exchanges may be switched on or off at calculation
time.
Tick this box if you wish to include Room Data auxiliary ventilation air exchanges in the Heat
Loss calculation.
Air exchanges are specified in Room Data in terms of a Maximum Value and a Variation Profile.
In Heat Loss the Variation Profile requires interpretation because the calculation does not
involve the time variable. The assumption is that the exchange rate takes the Maximum Value
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unless the profile is ‘Off continuously’ or a formula profile (which is not supported by Heating
Loads), when it takes the value zero.
3.1.3 Natural ventilation air exchange
Tick this box if you wish to include Room Data natural ventilation air exchanges in the Heating
Loads calculation.
Variation Profiles for natural ventilation are interpreted as for mechanical ventilation.
3.1.4 Include local and (when link ticked opposite) SunCast sky shielding
Tick this box if you wish the analysis to make allowance for the sky shielding effects of local
shades and shading objects analysed by SunCast. Under heating design conditions the sky
temperature will be below the ambient air temperature, and shielding surfaces from the sky
therefore has the effect of reducing heat loss.
3.1.5
Include DHW?
If you tick this box the heating loads calculated for Apache Systems will include the Domestic
Hot Water demand for each room.
Select ‘Use peak values’ to set DHW demand to the peak value in the room, or ‘Use time
settings below’ to set it according to the demand at the indicated time of day and year.
3.1.6 Time settings for profiles
The profile settings determine whether heating is available in each room. If the heating profile
is off at the specified hour, week day and month there is assumed to be no heating. In the case
of annual profiles the profile is evaluated for the indicated weekday in the central week of the
month.
3.1.7 Calculate
Click on this button to start the ASHRAE Loads Calculation.
3.1.8 Save & exit
Click on this button to leave the ASHRAE Loads dialog and save the data.
3.1.9 Close
Click on this button to leave the ASHRAE Loads interface.
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4 Cooling Loads
Cooling Loads calculates room cooling loads and free-floating temperatures using the ASHRAE
Heat Balance Method.
The calculation is carried out for one design day in each of a user-selected range of months,using weather data provided in APlocate. The calculation takes into account the timing and
nature of each gain, applying the appropriate radiant fraction to all sources of heat and cooling.
Inter-room dynamic conduction and ventilation heat transfer is accounted for. Glazing solar
transmission properties are treated using an analysis based on the Fresnel equations. At the
user’s option the effects of ventilation air exchanges and external solar shading, as calculated
by SunCast, may be incorporated.
Vista presents the Cooling Loads results in tabular or graphical form in a variety of formats.
Gains are broken down by heat transfer mechanism and by type (sensible or latent). Results
may be displayed by room, by zone or totalled over the building and peak loads are identified.
Various measures of room temperature are displayed, together with room relative humidity.
Data may be exported to other applications.
For a description of the calculation methods used in Cooling Loads see ApacheLoads Methods.
4.1
Interface for Cooling Loads Calculation
4.1.1 Cooling Loads Calculation
Tick this box to include a Cooling Loads calculation when you click on Calculate.
4.1.2 Auxiliary ventilation air exchange
Air exchanges specified in Room Data are divided into three categories: infiltration, mechanical
ventilation and natural ventilation. Any infiltration air exchanges are included unconditionally,
but mechanical and natural ventilation air exchanges may be switched on or off at calculation
time.
Tick this box if you wish to include Room Data mechanical ventilation air exchanges in the
Cooling Loads calculation.
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4.1.3 Natural ventilation air exchange
Tick this box if you wish to include Room Data natural ventilation air exchanges in the Cooling
Loads calculation.
4.1.4 SunCast Link?
Tick this box to include the effects of external solar shading, as calculated by SunCast or
SunCast Lite, in the Cooling Loads calculation. The SunCast shading data can also be applied to
the calculation of Heating Loads, where it is used to model the effects of sky shielding.
It is important to ensure that the shading data is kept up to date with any changes to the
building geometry. The shading calculations should be repeated after any such changes.
4.1.5 Design Day (for profiles)
The Cooling Loads calculation is carried out for one design day per month. Indicate which day of
the week is to be used to set the profiles used in Cooling Loads for casual gains, ventilation
rates and (if appropriate) temperature boundary conditions.
4.1.6 Calculation Period
Select the months for which Cooling Loads calculations are required.
4.1.7 Save & exit
Click on this button to leave the ASHRAE Loads dialog and save the data.
4.1.8 Calculate
Click on this button to start the Heating and Cooling Loads calculations.
4.1.9 Cancel
Click on this button to leave the ASHRAE Loads interface.
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5 Simulation (Heat Balance Method) settings
5.1.1 Simulation Options
Options for the simulation, see ApacheSim User Guide for details
5.1.2 Output Options
Options for output to the results viewer Vista, see ApacheSim User Guide for details.
5.1.3 Simulation time step
Specify the time step to be used in the simulation. A time step of 10 minutes is suitable for
most building simulations. For ASHRAE Loads calculations the reporting interval is fixed at 60
minutes.
5.1.4 Preconditioning
A period of preconditioning is necessary to ensure that the building enters the simulation
period in a realistic thermal state. Preconditioning is necessary because of heat storage in the
building fabric. For lightweight buildings a preconditioning period of 10 days is sufficient. For
heavyweight buildings as much as 30 days or more may be needed. The appropriate period of
preconditioning may be established by increasing the number of preconditioning days until the
effect of further increments produces a negligible change in the first day’s simulation results.
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6 Autosizing settings
6.1
Interface for Autosizing settings
6.1.1 Re-zero autosized parameters
Auto-sized parameters are the parameters located in the Room Data / Apache Systems dialog
that are sized during ApacheLoads or ApacheCalc calculations. Re-zero sets the values back to
zero before a new calculation.
6.1.2 Undo last autosize
Undo last autosize resets the autosized parameters to the previous calculated value.