Variation in System Performance while Sorting DEF Heating Hardware Options 2018-01-1813
The desire to reduce NOx at low ambient temperatures drives the use of heating methods to make DEF available by thawing the solution in the tank. Methods to validate modelling used to design hardware options require testing to gauge the accuracy of the prediction. Using a climatic chassis dynamometer (CCD) to demonstrate the guidance procedure set by the Environmental Protection Agency (EPA) is expensive and time consuming. A method of utilizing a flow controlled cooling supply combined with a standard cold chamber is described as a precursor to running the demonstration in the CCD. Testing multiple quantities of design iterations produced unexpected variation in the results. The sources of the variation and modifications taken to minimize them are discussed and presented. Test to test control of coolant flow, coolant temperature, and specific chamber temperature inconsistencies were found to be critically important to a successful effort. Several design iterations were compared with varying degrees of success. The method was modified as variation between tanks of the same design was noted. System description details as well as modifications to the process are discussed. A design that maximizes heat transfer to the DEF pick up area while providing enough heat to melt the remainder of the volume was found to clearly out-perform the others. Test apparatus details are described. The DEF heating loop system is exposed to varying temperatures and flows in the truck. Selection of a representative coolant flow and temperature is discussed. The EPA certification test method options are referenced. Control parameters are defined with the intent of demonstrating a test practice that minimizes CCD time and ultimately accurately predicts hardware performance on the certification test.