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apps:biomet_pmv [2014/09/15 13:39] – enviadmin | apps:biomet_pmv [2017/11/10 09:25] (current) – external edit 127.0.0.1 | ||
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====== PMV/PPD ====== | ====== PMV/PPD ====== | ||
- | The **PMV Model** (=Predicted Mean Vote Model) is probably the best know human thermal comfort model especially for indoor applications. It is based on Fangers (1972) comfort model and relates the energy balance of the human body with the humans thermal impression using a straight empirical function (see below). PMV was originally developed for steady-state indoor situations, but by extending the exergy | + | The **PMV Model** (=Predicted Mean Vote Model) is probably the best know human thermal comfort model especially for indoor applications. It is based on Fangers (1972) comfort model and relates the energy balance of the human body with the humans thermal impression using a straight empirical function (see below). PMV was originally developed for steady-state indoor situations, but by extending the energy |
- | PMV is, like most other thermal comfort indices, a stationary value. This means that the assessed person is assumed to be exposed long enough to a constant climate situation until all energy exchange processes at the human body have become stationary (if possible). While this the normal case for a person in an indoor environment, | + | PMV is, like most other thermal comfort indices, a stationary value. This means that the assessed person is assumed to be exposed long enough to a constant climate situation until all energy exchange processes at the human body have become stationary (if possible). While this is the normal case for a person in an indoor environment, |
In addition to the PMV value, ENVI-met BioMet provides the associated **PPD value** (// | In addition to the PMV value, ENVI-met BioMet provides the associated **PPD value** (// | ||
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{{ :: | {{ :: | ||
- | But as the PMV value is a mathematical function of the local climate, in most applications it can reach also values above or below the [-4] - [+4] values, althouth these are off scall of the original Fanger experimental data. | + | But as the PMV value is a mathematical function of the local climate, in most applications it can reach also values above or below the [-4] - [+4] values, althouth these are off scale of the original Fanger experimental data. |
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=== Required input === | === Required input === | ||
- | **Meteorological variables**, | + | **Meteorological variables**, |
* Air temperature $T_a$ | * Air temperature $T_a$ | ||
* Mean radiant temperature $T_{mrt}$ | * Mean radiant temperature $T_{mrt}$ | ||
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* Clothing insulation $I_{clo}$ | * Clothing insulation $I_{clo}$ | ||
* $M$: Mechanical energy production of the body | * $M$: Mechanical energy production of the body | ||
- | * $\eta$: | + | * $\eta$: |
The PMV/PPD reference person is always 35 year old, male, with a height of 1.75 m and a weight of 75 kg. These assumptions cannot be modified in the PMV/PPD calculations. | The PMV/PPD reference person is always 35 year old, male, with a height of 1.75 m and a weight of 75 kg. These assumptions cannot be modified in the PMV/PPD calculations. | ||
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== Scaling terms == | == Scaling terms == | ||
- | * $\mathbf{0.028+0.303\cdot (...)}$: \\ Emperical | + | * $\mathbf{0.028+0.303\cdot (...)}$: \\ Empirical |
== Body energy production == | == Body energy production == | ||
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* $f_{cl}$: Enlargement factor of body area due to clothing layer with $f_{cl}=1.0+I_{cl}\cdot 0.15$ with $I_{cl}$: clothing heat insulation in [clo]. \\ | * $f_{cl}$: Enlargement factor of body area due to clothing layer with $f_{cl}=1.0+I_{cl}\cdot 0.15$ with $I_{cl}$: clothing heat insulation in [clo]. \\ | ||
* $T_{cl}$ is the surface temperature of the clothing layer given in [K] | * $T_{cl}$ is the surface temperature of the clothing layer given in [K] | ||
- | * $T_{mrt}$ is the Mean Radiative Temperature of the surounding | + | * $T_{mrt}$ is the Mean Radiative Temperature of the surrounding |
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Solving the PMV equation is simple once the meteorological parameters and the personal settings are known and defined. The only non-linear term in the equation is the estimation of the clothing temperature $T_{cl}$ as $R$ and $C$ are depending on $T_{cl}$ while $T_{cl}$ itself is defined using both $R$ and $C$. | Solving the PMV equation is simple once the meteorological parameters and the personal settings are known and defined. The only non-linear term in the equation is the estimation of the clothing temperature $T_{cl}$ as $R$ and $C$ are depending on $T_{cl}$ while $T_{cl}$ itself is defined using both $R$ and $C$. | ||
- | This recursive dependency must be solved | + | This recursive dependency must be solved |
- | ==== Extention | + | ==== Extension |
- | As mentioned above, the concept of PMV/PPD as established by Fanger (1982) was designed for indoor applications. This did affect two fundamental aspects of the PMV mode: the design of the equations and the transition from energy balance units to comfort votes. | + | As mentioned above, the concept of PMV/PPD as established by Fanger (1972) was designed for indoor applications. This does affect two fundamental aspects of the PMV mode: the design of the equations and the transition from energy balance units to comfort votes. |
- | First, using the clothing surface temperature as the only environment sensitive variable may be acceptable under office conditions in the absence of direct sun light and almost no ventilation. In an outdoor setting in warm to hot climates, relevant fractions of the human body are not covered by clothing but are exposed to the outdoor | + | First, using the clothing surface temperature as the only environment sensitive variable may be acceptable under office conditions in the absence of direct sun light and almost no ventilation. In an outdoor setting in warm to hot climates, relevant fractions of the human body are not covered by clothing but are exposed to the outdoor |
- | Secondly, the PMV equation relates physical values (energy balance) to a personal comfort | + | Secondly, the PMV equation relates physical values (energy balance) to a personal comfort |
Despite these problems, PMV in its outdoor version is able summarize the effects of air temperature, | Despite these problems, PMV in its outdoor version is able summarize the effects of air temperature, |