Medical treatment system and methods using a plurality of fluid lines

A heating system for a peritoneal dialysis apparatus comprising:

• a heater bag containing dialysate solution and positioned on a heater pan;
• a pumping apparatus configured to pump dialysate into and out of the heater bag;
• an electrical heating element to heat the heater pan;
• one or more heater pan temperature sensors to detect a temperature of the heater pan;
• a dialysate temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to measure a dialysate temperature of dialysate in the heater bag;
• and
• a controller programmed to perform an inner control loop process that modulates electrical power provided to the heating element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target dialysate temperature and the dialysate temperature as measured by the dialysate temperature sensor.

A liquid heating system comprising:

• a heater bag containing a liquid and positioned on a heater pan;
• a pumping apparatus configured to pump liquid into and out of the heater bag;
• an electrical heating element to heat the heater pan;
• one or more heating pan temperature sensors to detect a temperature of the heater pan;
• a liquid temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to detect a liquid temperature of liquid in the heater bag;
• and
• a controller programmed to perform an inner control loop process that modulates electrical power provided to the heater element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target liquid temperature and an equilibrium temperature, wherein
• the equilibrium temperature is a weighted average of the liquid temperature and the heater pan temperature, the liquid temperature being weighted by a thermal capacitance, mass, or volume of liquid present in the heater bag, and the heater pan temperature being weighted by a thermal capacitance, mass, or volume of the heater pan.

A liquid heating system comprising:

• a heater bag containing a liquid and positioned on a heater pan;
• a pumping apparatus configured to pump liquid into and out of the heater bag;
• an electrical heating element to heat the heater pan;
• one or more heating pan temperature sensors to detect the temperature of the heater pan;
• a liquid temperature sensor mounted in the heater pan, thermally isolated from the heater pan, and configured to contact an outer surface of the heater bag to detect a liquid temperature of liquid in the heater bag;
• and
• a controller programmed to perform an inner control loop process that modulates electrical power provided to the heater element to achieve a target heater pan temperature as measured by the one or more heater pan temperature sensors, and programmed to perform an outer control loop process that determines the target heater pan temperature based on a difference between a pre-determined target liquid temperature and an equilibrium temperature, wherein
• the equilibrium temperature is a weighted average of the liquid temperature and the target heater pan temperature, the liquid temperature being weighted by a thermal capacitance, mass, or volume of liquid present in the heater bag, and the target heater pan temperature being weighted by the thermal capacitance, mass, or volume of the heater pan.