Modeling of Geothermal Heat Exchangers
Date Issued
2013
Abstract
Heat pumps (HP) attain higher efficiencies and save energy when they
are coupled to ground heat exchangers (GHEs). For this reason we
compare, by modeling, the efficiency of the vertical and horizontal
GHEs which are two basic types. The modeling of the vertical heat
exchanger is represented by two tube lines of 100 m in length,
embedded in four different types of ground with an additional bottom
base. The horizontal heat exchanger consists of four tube lines, 50 m in
length each, embedded in three ground layers. The simulation results of
the vertical GHE are validated by comparison to a measured set of data
showing very good agreement. Further simulations with the vertical GHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower mean GHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower meanGHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower mean temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous operation and 24°C initial ground temperature, show that the mean operation and 24°C initial ground temperature, show that the mean fluid temperature can stay below that of the vertical GHE if the center-to-center distance of the tubes increases to 1 .
are coupled to ground heat exchangers (GHEs). For this reason we
compare, by modeling, the efficiency of the vertical and horizontal
GHEs which are two basic types. The modeling of the vertical heat
exchanger is represented by two tube lines of 100 m in length,
embedded in four different types of ground with an additional bottom
base. The horizontal heat exchanger consists of four tube lines, 50 m in
length each, embedded in three ground layers. The simulation results of
the vertical GHE are validated by comparison to a measured set of data
showing very good agreement. Further simulations with the vertical GHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower mean GHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower meanGHE show, as expected, that when the initial ground temperature rises
the mean temperature of the heat exchanger fluid increases as well in a
linear relationship. For a 50-hour continuous operation, the inlet and
outlet fluid temperatures are computed for certain ground temperatures.
Comparisons between the horizontal and vertical GHEs reveal that
under the same operating conditions and center-to-center distances of
the tubes, the vertical heat exchanger keeps a much lower mean temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous temperature because the initial ground temperature at the buried tube
depth is always higher than that of the vertical GHE. Because of this
observation one would assume that the vertical GHE is more efficient
than the horizontal. Instead, in a proper design, one could increase the
distance between the tube centres and in this way decrease the mean
temperature of the tube fluid. Simulations, for a 50-hour continuous operation and 24°C initial ground temperature, show that the mean operation and 24°C initial ground temperature, show that the mean fluid temperature can stay below that of the vertical GHE if the center-to-center distance of the tubes increases to 1 .