Design Issues

The first design issue that was encountered was determining the size, length, and type of copper tubing to be used for the device. Since one of the primary requirements of the device is size and weight, finding the most effective ratio of length of tubing, minimum bending diameter, coil height, coil diameter, and system efficiency.

 

The second design issue was the design and construction of the chimney (exhaust of gas) and housing system. The chimney system must be able to withstand the extreme temperatures expected during the operation of the device. The housing of the device must allow the user to touch device during operation without the risk of injury to the user.

 

The final design issue was the ability to acquire necessary parts at a reasonable cost.

 

Calculated Parameters

Below (and in more detail in Appendix A Figures 4-12) are some of the critical calculations used in determining the size of tubing required for heating, the overall dimensions of the heating coil (which allows for future design of the housing) as well as the amount of energy required to heat the water to its desired setpoints (allows for sizing of the burner).

 

·       Length of 3/8” Type K copper tubing needed to achieve desired pressure drop: 137 ft.

·       Length of 3/8” Type K copper tubing needed to achieve desired heat transfer: 18 ft.

·       Overall dimension of coiled tubing (based on minimum bend radius of Type K copper tubing: 6” diameter, 18” height.

·       Heat required to achieve desired 55°F to 185°F temperature increase: 226,560 BTU/Hr.

 

Best Practices

Since this system is going to be connected to a gas heat source, the housing is going to be designed to minimize the risk that the end user will get burned (either by radiant heat from the coil or from direct contact with flame). Also, a pressure relief system will be incorporated in the event that the control valve is shut while the gas heat is still on and there is water still in the system. This will prevent the superheated vapor from bursting the copper tubes and injuring the end user.