Heat Loss from Open Water Tanks

Due to evaporation heat loss from open water tank as a swimming pools may be considerable

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The overall heat loss from an open water tank can be expressed as:

Q = Q_{evaporation fluid} + Q_{radiation fluid} + Q_{transmission through walls} (1)

The heat loss due to evaporation of water from a surface of an open tank is totally dominant at higher water temperatures. In general heat loss through insulated walls can be almost neglected. Major heat loss can be avoided by covering the surface.

Water Temperature (^oF) Load Calculator!	Heat Loss from Liquid Surface (Btu/ft²hr) Load Calculator!			Heat Loss Through Tank Walls (Btu/ft²hr) Load Calculator!
	Evaporation Loss	Radiation Loss	Total	Bare Steel Uninsulated	Insulated (inches)
	Evaporation Loss	Radiation Loss	Total	Bare Steel Uninsulated	1	2	3
90	80	50	130	50	12	5	4
100	160	70	230	70	15	8	6
110	240	90	330	90	19	10	7
120	360	110	470	110	23	12	9
130	480	135	615	135	27	14	10
140	660	160	820	160	31	16	12
150	860	180	1040	180	34	18	13
160	1100	210	1310	210	38	21	15
170	1380	235	1615	235	42	23	16
180	1740	260	2000	260	46	25	17
190	2160	290	2450	290	50	27	19
200	2680	320	3000	320	53	29	20
210	3240	360	3600	360	57	31	22

the values above are for 60 ^oF (15.6 ^oC) still ambient air

Example - Heat Loss from an open Water Tank

The heat loss from an open water tank with

water temperature: 150 ^oF
surface area: 10 ft²
un-insulated bare steel tank walls area: 50 ft²

can be estimated with values from the table above as:

Q_{(evaporation fluid + radiation fluid)} = (1040 Btu/(ft² hr)) (10 ft²)

= 10400 Btu/hr

Q_{transmission through walls}= (180 Btu/(ft² hr)) (50 ft²)

= 9000 Btu/hr

Q = Q_{(evaporation fluid +}_{radiation fluid)} + Q_{transmission through walls}

= (10400 Btu/hr) + (9000 Btu/hr)

= 19400 Btu/hr

Heat Loss from Water Surfaces Chart - Metric Units

Heat loss from Water Surfaces - Metric Units (pdf)

Heat loss are for open tanks in 60^oF still ambient air.

Heat Loss from Water Surfaces Chart - Imperial Units

Heat loss from Water Surfaces - Imperial Units (pdf)

T(^oC) = 5/9[T(^oF) - 32]
1 Btu/(ft²hr) = 3.1525 W/m²

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Heat Loss from Open Water Tanks

Due to evaporation heat loss from open water tank as a swimming pools may be considerable

Example - Heat Loss from an open Water Tank

Heat Loss from Water Surfaces Chart - Metric Units

Heat Loss from Water Surfaces Chart - Imperial Units

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