T H E R M A L P O L L U T I O N AND 0 2 T R A N S F E R
STREAM TEMPERATURE RESPONSE
TO THERMAL POLLUTION
V. NOVOTNY and P.A. KRENKEL*
*Dept. of Sanitary and Water Resources Engineering,
Vanderbilt University, Box 1670 - Station B, Nashville, Tennessee 37203, U.S.A.
INTRODUCTION
It is expected that by the year 2000, the production of electric energy in the United
States will be about nine times that of 1970. Both fossil fuel and nuclear power plants
require large amounts of cooling water for the dissipation of waste heat, the latter
discharging the greater amount of heat on an equivalent capacity basis. Because of the
relatively low thermal efficiency of either type of thermal power station, the larger part
of the heat produced is released through the cooling system into the aquatic and
atmospheric environment. Resulting increased temperatures in the receiving water may
have harmful effects, such as a shift in population of the ecosystem, death of aquatic
organisms beyond certain limiting temperatures, decreased waste assimilative capacity,
etc.
It is obvious that this problem requires immediate attention, and furthermore, that all
consequences of heated water discharges should be investigated. Major considerations are
the determination of river assimilative capacity for heat, the thermal behavior of water in
rivers, and the response in water temperature that can be expected from added waste heat
with respect to certain meteorological conditions.
BASIC TEMPERATURE RELATIONS IN STREAMS
Although heat transfer in flowing waters differs in some respects from that occurring
in lakes and reservoirs, it has been common practice to apply the results obtained in
studying evaporation and heat transfer in lakes (e.g. the classical Lake Hefner Study -
U.S. Geological Survey - 1954) to those in streams. The following simple comparison
demonstrates significant differences between heat dissipation and evaporation in lakes
and rivers:
Lakes
Rivers
Little turbulence in water body
High degree of turbulence
Lower turbulence level at water surface
High degree of turbulence at water surface
Water body is thermally stratified
Minimal thermal stratification
Low degree of uniformity
High degree of uniformity
Topographical differences
Size difference
The equation describing heat transfer in rivers can be written as:
3T Π τ 3 ! ΐ + ΐ ί 3 Τ
OL
Qs - Q
m
äT"
D L 3x
2 + U 3 x ~ ~ H
( T s -
T ) - H ^ °
( 1 )
STREAM TEMPERATURE RESPONSE
TO THERMAL POLLUTION
V. NOVOTNY and P.A. KRENKEL*
*Dept. of Sanitary and Water Resources Engineering,
Vanderbilt University, Box 1670 - Station B, Nashville, Tennessee 37203, U.S.A.
INTRODUCTION
It is expected that by the year 2000, the production of electric energy in the United
States will be about nine times that of 1970. Both fossil fuel and nuclear power plants
require large amounts of cooling water for the dissipation of waste heat, the latter
discharging the greater amount of heat on an equivalent capacity basis. Because of the
relatively low thermal efficiency of either type of thermal power station, the larger part
of the heat produced is released through the cooling system into the aquatic and
atmospheric environment. Resulting increased temperatures in the receiving water may
have harmful effects, such as a shift in population of the ecosystem, death of aquatic
organisms beyond certain limiting temperatures, decreased waste assimilative capacity,
etc.
It is obvious that this problem requires immediate attention, and furthermore, that all
consequences of heated water discharges should be investigated. Major considerations are
the determination of river assimilative capacity for heat, the thermal behavior of water in
rivers, and the response in water temperature that can be expected from added waste heat
with respect to certain meteorological conditions.
BASIC TEMPERATURE RELATIONS IN STREAMS
Although heat transfer in flowing waters differs in some respects from that occurring
in lakes and reservoirs, it has been common practice to apply the results obtained in
studying evaporation and heat transfer in lakes (e.g. the classical Lake Hefner Study -
U.S. Geological Survey - 1954) to those in streams. The following simple comparison
demonstrates significant differences between heat dissipation and evaporation in lakes
and rivers:
Lakes
Rivers
Little turbulence in water body
High degree of turbulence
Lower turbulence level at water surface
High degree of turbulence at water surface
Water body is thermally stratified
Minimal thermal stratification
Low degree of uniformity
High degree of uniformity
Topographical differences
Size difference
The equation describing heat transfer in rivers can be written as:
3T Π τ 3 ! ΐ + ΐ ί 3 Τ
OL
Qs - Q
m
äT"
D L 3x
2 + U 3 x ~ ~ H
( T s -
T ) - H ^ °
( 1 )