BTU/GPM Delta T Calculator

Inputs

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Measured or planned liquid flow through the coil, heat exchanger or hydronic loop.
gpm
Temperature drop or rise across the coil or heat exchanger. Use the absolute temperature difference.
°F
Heating or cooling load used to back-solve required flow and required Delta T.
Btu/h
Fluid density at the loop operating temperature. Water near room temperature is about 998 kg/m3.
lb/ft³
Fluid heat capacity. Water is about 4.186 kJ/kg-K, or 1.00 Btu/lb-F.
Btu/lb-F

Results

Default result
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Hydronic load(q)
99,930Btu/h
Pass

q = rho * cp * Q * Delta T using the entered fluid properties.

Also computed

Flow for target load(Q_req)Pass10.01gpm

Flow needed to carry the target load at the entered Delta T and fluid properties.

Delta T for target load(Delta T_req)Pass20.01°F

within a common hydronic screening band for many heating and chilled-water loops

Load margin(q - q_t)Pass−74.53Btu/h

entered flow and Delta T are close to or above the target load

Flow margin(Q - Q_req)Pass−0.007459gpm

entered flow is close to or above the back-solved required flow

Mass flow(m_dot)83.29lb/min

500 x GPM x Delta T load(q_500)100,000Btu/h

Hydronic water shortcut: BTU/h = 500 x GPM x Delta F.

Hydronic heat transfer preview: 99,925 BTU per hour, 10.0 GPM required at target loadHydronic loop heat transferFlow x fluid heat capacity x Delta T gives sensible loop load.actual load99,925BTU/hflow for target load10.0 GPMDelta T for target load20.0 Fwater shortcut difference0.1%Target coverageWater shortcut fitScreen only. Final hydronic design still needs coil/boiler/chiller data, pump curves, glycol properties, control valves, balancing and code review.
Method notes 3 notes
  • Main formula: q = rho * cp * Q * Delta T. Flow is converted to m3/s, cp to J/kg-K and the result to W or BTU/h.
  • For standard water in imperial units, the same relation is often approximated as BTU/h = 500 x GPM x Delta F.
  • This is sensible hydronic heat transfer only. Final design still needs coil, boiler/chiller, pump curve, control valve, balancing, glycol, fouling and code/manufacturer checks.

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