saeranv's profile - activity

@shorowit, great, thanks!

Question about Cw, the "Opening effectiveness" factor for ZoneVentilation:WindandStackOpenArea The formula given in the

Question about Cw, the "Opening effectiveness" factor for ZoneVentilation:WindandStackOpenArea The formula given in the

@mattkoch why not just manually output the ideal air zone supply cooling/heating timeseries, sum across the zone loads p

@mattkoch why not just manually output the ideal air zone supply cooling/heating timeseries, sum across the zone loads p

Thanks for clearing it up. I should have caught that, H is specific enthalpy in J/kga, not enthalpy in J.

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

@rraustad, can you clarify this equation: Qcoil = Mdot,zone * (Hcoil,in - Hcoil,out) Is H enthalpy (in J)? If so,

I'm not familiar with what Appendix G requires for sizing runs, but I've always seen the ideal loads air system used for

Since the peak loads are used to size the boiler capacity, it seems unlikely to me that the boiler capacity could be cor

Since the peak loads are used to size the boiler capacity, it seems unlikely to me that the boiler capacity could be cor

Are you sure there's only one boilers assigned to your the high-rise? The coincidental building peak capacity is 92 MW,

Are you sure there's only one boilers assigned to your the high-rise? The building peak capacity 92 MW, but the boiler c

Are you sure there's only one boilers assigned to your the high-rise? The building peak capacity 92 MW, but the boiler c

I apologize, yes you're right. I thought there was a regression being done at some point but I must be confusing this wi

No, you'll have to find the detailed inputs for the actual window construction you're representing and build up a layer

The Simple Glazing model uses a much more complex calculation to derive the window U-Value then Rw = 1/U - Ri - Re. It h

If there's no explicit exceptions mentioned in the documentation of specific algorithms, I see no reason to assume they

I can only say that, based on my interpretation of the EP reference, the answer is yes for all three, but caveat: I have

For Q2 and Q3 they explicitly mention "Only local outdoor air temperature and wind speed are currently calculated becaus

I can only say that, based on my interpretation of the EP reference, the answer is yes for all three, but caveat: I have

I think the Zone Outdoor Air Drybulb is the Site Outdoor Air Drybulb recalculated to account for the temperture differen

Yeah importing an idf file might have errors. I've never run into errors building the model from scratch in Honeybee (as

The Thermal Load Balance provides a monthly breakdown of hourly loads from an annual simulation, not peak loads (there's

This is very interesting. However I think to properly understand the usefulness, it would be helpful to clarify where yo

Specifically, the Thermal Load Balance component, as seen here: https://docs.ladybug.tools/hb-energy-primer/components/6

Good question, at that level of detail my intuition about what is happening isn't strong. Can you share the hourly times

Is this just the impact of thermal lag creating slightly different interior/exterior temperature gradients, which in tur

Since EP uses (by default) finite difference approximations to calculate the change in zone temperature, I believe the o

Yeah, there's two I can think of. The outdoor air temperature used for surface conduction and convection calculations is

Yeah, there's two I can think of. The outdoor air temperature used for surface conduction and convection calculations is

Yeah, there's two I can think of. The outdoor air temperature used for surface conduction and convection calculations is

The outdoor air temperature used for surface conduction and convection calculations is modified to account for the air t

What is the correct way to calculate U-value impact of the column? Typically we assumes surfaces transfer heat in 1D (pe

This can be further broken down into two questions, first, what is the best way to model interzone airflow through Air Walls with the EnergyPlus AirflowNetwork, and secondly, (assuming cracks are a good way to achieve interzone air flow) how can I derive an appropriate flow coefficient for this scenario?

1. What is the best way to model interzone airflow through Air Walls with the AFN?

The EnergyPlus 'Tips and Tricks' section on Air wall, Open air connection suggests using a large vertical opening between zones with the AFN, which seems to realistically capture both the volume and two-way flow of air between two zones open to each other. However I have since learned that EnergyPlus does not support using the SimpleOpening with BuildingSurfaces (only with FenestrationSurfaces). Our team would like to use the Air Wall, rather then a FenestrationSurface, to capture radiant exchange between zones.

The next best strategy seems to be to model the airflow using an extremely leaky crack. There seems to be some precedent for this, referenced in the DetailedOpening Input/Output documentation, which suggests using an AFN Crack with a "large air mass flow coefficient" for large horizontal openings, since regular horizontal openings won't model two-way flow in exterior surfaces. While this method won't capture the two-way flow that occurs in the AFN SimpleOpening, its seems like I should be able to reproduce the volume (with a correctly chosen flow coefficient), while maintaining the radiant exchange properties of the Air Wall.

2. How to derive a Cq?

If the second strategy seems reasonable, the second question is: what is the best approach to derive a mass flow coefficient that would replicate the air flow quantity of a large-ish vertical opening? My instinct is to try and approximate the mass flow coefficient from the formula used for the surface EffectiveLeakageArea?

The derivation I have in mind is as follows:

The crack formula is: 

m = Cq * dP^n 

where: 

m_crack = mass flow rate kg/s 

Cq = mass flow coefficient 

dP = pressure difference across crack 

n = mass flow exponent

The ELA formula is:

So to derive the Cq from the ELA formula:

m_crack = m_ela  

Cq * dP^n = ELA * Cd * sqrt(2 * density) * dP_r^(0.5 - n) * dP^n 

The dP^n cancels out, I assume n = 0.5 (for turbulent flow) which makes dP_r(0.5-n) = 1, and rearrange to get: 

Cq = ELA * Cd * sqrt(2 * density)

So I plug in a large opening area for the ELA parameter, and some assumption for air density to get the Cq for the interzone crack. I realize I can use the Surface:ELA object to achieve the same result, but we've already programmed infiltration into our software using the AFN Crack method, so would like to avoid introducing a new EP object, if possible.

Please let me know if this seems reasonable, of if there's a better way of modeling interzone air mixing with an Air Wall. Thanks in advance.

In EnergyPlus, the ZoneInfiltration objects are not calculated when using the AirflowNetwork (AFN) for the MultiZoneWithoutDistribution control (amongst others). In a previous post[1] it's been suggested that the way to model infiltration in the AFN method, based on the ZoneInfiltration object, is to replace the infiltration objects with enough AFN leakage to get the equivalent infiltration amount of the ZoneInfiltration object. Is there a calculation to figure out this type of conversion out mathematically?

For context, I'm working on a software project where our zones all contain ZoneInfiltration:DesignFlowRate objects, using the Flow/ExteriorWallArea calculation method[2]. So we have the volumetric flow rate m3/s-m2, schedule, constant, temperature and velocity coefficients already defined. We want to include an option to use the AFN for mixed-mode, or purely passive cooling. When this translation is done, we'd like the infiltration rates to be equivalent (or somehow logically translated) from our ZoneInfiltration objects.

Does a formula/look-up table exist to convert the DesignFlowRate to an AFN leakage component, like the AFN:MultiZone:Surface:Crack or AFN:MultiZone:EffectiveLeakageArea objects?

[1] https://unmethours.com/question/39416...

[2] https://bigladdersoftware.com/epx/doc...