Heat Release Rate Detection Calculator

Calculate the heat release rate needed for heat/smoke detector activation using ceiling jet correlations.

Input Parameters

Results

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Required HRR
kW
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Ceiling Jet Temp
deg F
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Ceiling Jet Velocity
ft/s
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Est. Activation Time
sec
Note: Based on Alpert unconfined ceiling jet correlations. RTI values: fast-response sprinklers ~25-50, standard sprinklers ~80-200, heat detectors ~30-300. Lower RTI means faster response.

Reference

Alpert Ceiling Jet Correlations: For r/H > 0.18: dT = 5.38*(Q/r)^(2/3) / H For r/H <= 0.18: dT = 16.9*Q^(2/3) / H^(5/3) Velocity: Uj = 0.195*Q^(1/3)*H^(1/2) / r^(5/6) Activation Time: tau = RTI / sqrt(Uj) Time = tau x ln((Tjet-Tamb)/(Tjet-Tact))