Infiltration

Infiltration is the unintended air exchange between an interior space and the exterior. In SIMPLE, infiltrations are added to the intended ventilation.

This group of objects allow defining infiltration on different ways. Which variety is better will depend on the information available and the kind of building.

Examples

.spl

// Note that Infiltration is always attached to a Space
Space {
    name: "Bedroom", 
    volume: 42, // volume in m3. 
    infiltration: { // <- Define the infiltration
        type : "Doe2", 
        flow : 0.24,
    }
}

.json

{
    "type": "DesignFlowRate",
    "a": 1.0,
    "b": 0.0,
    "c": 0.04,
    "d": 0.0,
    "phi": 1.2
}

{
    "type": "Constant",
    "flow": 1.2
}

Note: This object cannot be declared by itself in a SIMPLE model, as it is always embeded on a Space

Supported Variants

Constant

A contant infiltration, specified in m3/s

Full Specification

Infiltration {
	type : "Constant", // this should not change
	flow : number
}

Blast

It is the same as the DesignFlowRate infiltration object, but specifying the default values from BLAST, as described in the EnergyPlus' Input Output reference

Full Specification

Infiltration {
	type : "Blast", // this should not change
	flow : number
}

Doe2

It is the same as the DesignFlowRate infiltration object, but specifying the default values from DOE-2 as described in the EnergyPlus' Input Output reference

Full Specification

Infiltration {
	type : "Doe2", // this should not change
	flow : number
}

DesignFlowRate

Sets the infiltration to the DesignFlowRate values using an arbitrary set of values. This option is based on EnergyPlus' object of the same name.

The flow $phi$ (in $m^3/s$) is calculated from the parameters $A$, $B$, $C$, $D$ and $ph{i}_{design}$ as follows:

$$\begin{gathered} phi= \\ ph{i}_{design}(A+B|T_{space}-T_{outside}|+C \\ times{W}_{speed}+D \\ times{W}_{speed}^2) \end{gathered}$$

The inputs to this object are $A$, $B$, $C$, $D$, $ph{i}_{design}$ .

Full Specification

Infiltration {
	type : "DesignFlowRate", // this should not change
	a : number
	b : number,
	c : number,
	d : number,
	phi : number,
}

EffectiveAirLeakageArea

Sets the infiltration based on EffectiveLeakageArea as described in the EnergyPlus' Input Output reference. This variant of infiltration requires the space to be part of a Building

The infiltration rate—in $m^3/s$—is calculated based on the following equation:

$$\begin{gathered} phi= \\ frac{A}_{L}1000 \\ sqrt{C}_s \\ DeltaT+C_w{W}_{speed}^2 \end{gathered}$$

where:

• $A_L$ is the effective air leakage in $c{m}^2$ @ 4Pa (NOTE THAT THE INPUT IS IN M2)
• $C_s$ is the coefficient for stack induced infiltration
• $C_w$ is the coefficient for wind induced infiltration

The only input to this object is the effecctive air leakage, $A_L$, in $c{m}^2$ @ 4Pa. The other parameters—$C_s$ and $C_w$—are derived based on the required Building object associated with the Space that owns this Infiltration. For this to work, the associated Building needs to have been assigned the fields n_storeys and a shelter_class (which allow calculating $C_s$ and $C_w$) OR the properties of stack_coefficient (i.e., $C_s$) and wind_coefficient (i.e., $C_w$).

Note: The EffectiveAirLeakageArea object is appropriate for buildings of 3 storeys or less.

Example

Building {
    name: "Art Deco Building", 
    n_storeys: 2,
    shelter_class: "Urban",
}

Space {
    name: "Kids Bedroom",
    volume: 19.23, 
    infiltration: {
      type : "EffectiveAirLeakageArea",
      area: 0.0496, // this is roughly 22cm x 22cm
    },
    building: "Art Deco Building"
}

Values for $A_L$

(source of this example: Sherman and Grimsrud (1980) Infiltration-Pressurization correlation: Simplified physical modeling). Conference of American Society of Heating, Refrigeration and Air Conditioning Engineers

Ideally, the value from $A_L$ should come from a blower-door test. When doing one of these, you can get a table like the following:

This data can be fitted in a model with the shape:

$$\begin{gathered} Q=K{ \\ DeltaP}^b \end{gathered}$$

In this case, the values for $K$ and $b$ are $0.0555$ and $0.6032$, respectively.

Evaluating this model at $4Pa$, we get an air flow $Q$ of $0.128m^3/s$.

To calculate $A_L$ we now need to use this data in the following equation, which relates air flows through openings of size $A_L$:

$$\begin{gathered} Q=A_L \\ sqrt \\ frac2 \\ DeltaP \\ rho \end{gathered}$$

Where $rho$ is the air density of $1.2kg/m^3$. So, the estimated $A_L$ would be $0.0496m^2$

Full Specification

Infiltration {
	type : "EffectiveAirLeakageArea", // this should not change
	area : number
}