Abstract: Coolant systems, for power sources (e.g. internal combustion engines, fuel cells, and nuclear reactors) or microprocessors for example, are beneficially operated with coolant in a nucleate boiling state, but transitions to damaging film boiling are then possible. The disclosed coolant system includes a sensor, such as a thermocouple or thermistor, that provides a signal representative of fluctuations in the temperature at a heated surface. The signal also includes at least one parameter. A controller processes the signal to determine changes in the parameter of the signal and/or to determine the state of the coolant and can responsively change the coolant flow to avoid undesirable coolant states. For example, coolant flow can be changed by changing the output of a coolant pump. The controller can change coolant flow automatically, or a signal can be provided to an operator that an undesirable coolant state change is imminent or has occurred, thereby allowing operator intervention.

Abstract: Heat transfer in coolant circuits, as in an internal combustion engine for example, can be beneficially enhanced by maintaining the coolant in a nucleate boiling state, but undesirable transitions to a film boiling state are then possible. The disclosed coolant circuit has selected surface(s) that have a tendency to experience high heat flux in comparison to adjacent surfaces in the coolant circuit. These surfaces are provided with a surface configuration, such as a matrix of nucleation cavities, which has a tendency to inhibit a change in boiling state. The surface configuration can be provided on the parent coolant circuit surface or on a surface of an insert positioned in the coolant circuit. Thus, transitions to film boiling can be effectively avoided at locations in the coolant circuit that are susceptible to such transitions.

Abstract: Heat transfer in coolant circuits, as in an internal combustion engine for example, can be beneficially enhanced by maintaining the coolant in a nucleate boiling state, but undesirable transitions to a film boiling state are then possible. The disclosed coolant circuit has selected surface(s) that have a tendency to experience high heat flux in comparison to adjacent surfaces in the coolant circuit. These surfaces are provided with a surface configuration, such as a matrix of nucleation cavities, which has a tendency to inhibit a change in boiling state. The surface configuration can be provided on the parent coolant circuit surface or on a surface of an insert positioned in the coolant circuit. Thus, transitions to film boiling can be effectively avoided at locations in the coolant circuit that are susceptible to such transitions.

Abstract: Coolant systems, for power sources (e.g. internal combustion engines, fuel cells, and nuclear reactors) or microprocessors for example, are beneficially operated with coolant in a nucleate boiling state, but transitions to damaging film boiling are then possible. The disclosed coolant system includes a sensor, such as a thermocouple or thermistor, that provides a signal representative of fluctuations in the temperature at a heated surface. The signal also includes at least one parameter. A controller processes the signal to determine changes in the parameter of the signal and/or to determine the state of the coolant and can responsively change the coolant flow to avoid undesirable coolant states. For example, coolant flow can be changed by changing the output of a coolant pump. The controller can change coolant flow automatically, or a signal can be provided to an operator that an undesirable coolant state change is imminent or has occurred, thereby allowing operator intervention.