Copyright © 2009 Integrated Environmental Solutions Limited. All rights reserved
ASHRAE Members around the world recently received their 2017 Fundamentals Handbook. Most of us likely received the digital version on a CD. Many of the new updates will impact the HVAC load calculations, performed by mechanical designers day in & day out – there are new design LPDs, revised kitchen equipment resources, and additional climate data, among many other additions! Something that hasn’t changed: load calculation methods.
The 2017 edition of the Fundamentals Handbook defines only two load calculation methods: the Heat Balance Method (HBM) and Radiant Time Series (RTS). As part of the introduction, the radiant time series is categorized as “a simplification of the [heat balance] procedure”, but what exactly is the simplification?
Heat gain from the sun offers an illustrative example. Solar energy is absorbed by the exterior wall of a building and transfers to the inside of the building by conduction. Because the wall has thermal mass, that heat isn’t transferred immediately – there’s a conductive delay.
Solar energy is transmitted to the inside of the building through the window. Some of the heat is absorbed and reflected by the window, and the remainder is absorbed by the interior surfaces. When those surfaces later emit that heat by convection, cooling load is created in the room – there’s a radiative delay.
The Heat Balance Method calculates these time delay effects explicitly with some basic assumptions like uniform surface temperatures. There are no arbitrarily set parameters. Conductive, convective, and radiative heat balance is calculated directly for each surface within a room.
By contrast, the radiant time series (RTS) calculation uses radiant time factors and conduction time factors to distribute hourly heat gains over a 24 hour period instead of iteratively calculating the time delay effects. A table of time factors published in the Handbook determines how long heat is held by a wall or other surface before creating a cooling load in the space.
Whether heat balance method or radiant time series is used to calculate heating & cooling loads, computer software is nearly always employed. IES Virtual Environment (VE) software performs ASHRAE load calculations using the non-simplified Heat Balance Method, calculating heat balance and the resulting loads directly without time factors. To learn more about calculating loads for HVAC design using the VE, check out www.iesve.com/loads.
This week you may have noticed that we’ve changed how we name our software releases. The product formerly known as “VE 6.5” has taken a hit from the rebranding fist of justice and is now going by the moniker “VE 2012“.
So what does this mean for you, the user? Well by naming the releases in this way, it should make it very clear if you are using the most current version of the software or if you’re a little out of date.
And don’t worry, just because this one is called ‘VE 2012’ doesn’t mean we won’t be offering you regular updates, far from it! From here on in, we’ll simply be focusing on individual Module Feature Packs.
Well that’s the name change covered. Now let’s get to the awesome new features and capabilities that will be available with VE 2012. First up is the ModelViewerII, which features a new solar arc tool to visualize the sun’s position in relation to the 3D Model, new real-time shadows (with video capability) and greatly improved video and image creation.
VE 2012 contains some important new solar analysis features. VE-Pro Suncast users can now view solar intensity/exposure on a 3D model, determine their own parameters for analysis (such as time period and resolution) and quickly understand the intensity of the sun externally on the building faÃ§ade.
VE 2012 also includes other major new features including: ApacheHVAC enhancements, Daikin VRV Systems plug-in, Monodraught Windcatcher Performance Component, Trimble Plancal nova connection plus new Singapore and New Zealand compliance tools.
You can find out more about these features and all the other new enhancements included in VE 2012 here.
And you can visit our online Download Centre to “morph” your current software version to VE 2012 today.
PS — For those of you outside the UK & Ireland, Morph (pictured above) is an animated Plasticine stop motion character who was created in the 1970s by Aardman Animations, the people behind Wallace and Gromit.