DEF (Diesel Exhaust Fluid) tank assembly is a system that stores and dispenses DEF, a liquid used in selective catalytic reduction (SCR) systems to reduce nitrogen oxide emissions in diesel engines.

The design of a DEF tank assembly typically includes a tank made of a corrosion-resistant material such as high-density polyethylene (HDPE) or stainless steel, a dispensing system such as a pump or nozzle, and a control system to monitor the level of DEF in the tank and dispense the fluid as needed.

The tank should be designed to withstand the specific temperature and pressure requirements of DEF and to prevent contamination of the fluid. The tank should also be designed with an appropriate capacity to meet the needs of the diesel engine.

The dispensing system should be designed to accurately measure and dispense the DEF, and to prevent any leakage or spills. The control system should be able to monitor the level of DEF in the tank and provide alerts when the fluid is running low.

It's important to ensure that the DEF tank assembly complies with the regulations and standards of the industry and the environmental protection agency, including emissions standards and safety requirements.

The assembly should also be designed to be easily installed, maintained, and serviced. This might include features such as easy-to-access components, clear labeling, and a detailed manual for operation and maintenance.