Final answer:
The holding time in a plate heat exchanger is influenced by the specific heat capacities, flow rates, temperature difference, and thermal conductivity of the materials. Higher enthalpy changes in one of the fluids can result in longer holding times. The formula for heat transfer rates integrates these factors, determining the efficiency with which a heat exchanger operates.
Step-by-step explanation:
The length of holding time in a plate heat exchanger is determined by several factors related to the thermodynamics of the system. This concept is similar to the analysis of the enthalpy changes in phase transitions as depicted in Libre Texts where the length of time that temperature remains constant during a phase change is proportional to the magnitude of the enthalpy change.
In plate heat exchangers, the holding time is influenced by the specific heat capacities of the fluids being exchanged, the flow rates, the temperature difference driving the heat transfer, and the properties of the materials making up the plates. For instance, if one fluid has a high enthalpy change during its phase transition, this could result in a longer holding time.
Heat transfer rates are also a function of materials' thermal conductivity, as well as the dimensions and shape of the conducting paths. The heat transfer rate formula, confirmed by experiments, includes both these material properties and the geometrical characteristics of the system. Finally, the characteristic time is mentioned to explain the influence of inductance and resistance in a different context, indicating how system properties impact the response time of a process. While this is meant for electrical inductors, the idea can be loosely related to heat exchangers where the capacity and resistance to heat transfer results in a certain time behavior.