Waste heat from radioisotope thermal generators in spacecraft is transported to keep instruments warm by two-cylinder reciprocating pump powered by energy from warm heat exchange fluid. Each cylinder has thermally nonconductive piston, heat exchange coil, and heat sink surface

Sabelman, E. E.

English

NASA Technical Reports Server

December 1972
	 B72-10723 
NASA TECH BRIEF 
NASA Pasadena Office 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Thermal-Powered Reciprocating Pump
^ To Science 
Instruments 
Hot 
Fluid -
Check Valve 
Spring 
Piston 
Freon Vapor 
Heating Coil 
Freon Liquid 
Heat Sink
	
Volume 
The problem: 
Science and flight instruments in spacecrafts must 
be kept warm during missions in deep space. Radio-
isotope thermal generators in spacecrafts produce an 
abundance of waste heat which is normally allowed 
to escape into space; it would be desirable to trans-
port some of the waste heat by means of a heat ex-
change fluid to the cold instruments, but an electrical 
pumping system cannot be used because it would 
consume 10 watts of power. An alternative method 
for circulating the heat exchange fluid was required. 
The solution: 
A two-cylinder reciprocating pump which is 
powered by energy derived from the warm heat ex-
change fluid; reciprocating action in each of the cyl-
inders occurs because of alternate vaporization of a 
working fluid by the heat exchange fluid and conden-
sation by flow of the latent heat of vaporization to a 
heat sink. 
How it's done: 
The device consists of a pair of cylinders, each with 
a thermally nonconductive piston, a heat-exchange 
coil, and a heat sink surface. The cylinders are inter-
connected as indicated in the diagram, that is, the 
heat coil of one cylinder is connected to the intake of 
the other cylinder. In each cylinder, a working fluid 
(such as dichlorodifluoromethane) is trapped between 
the piston and the end of the cylinder which is in 
communication with a heat sink. 
As indicated in the diagram, the left piston is 
moving downward; this occurs because the working 
fluid in the cylinder is condensing at the cold surfaces 
in contact with the cylinder. The downward motion 
of the left-hand piston draws hot heat exchange fluid 
(continued overleaf) 
This document was prepared under the sponsorship of the National	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000722 2020-03-17T03:44:28+00:00Z
from the supply line through the heating coil in the 
right-hand cylinder and causes vaporization of the 
working fluid in the cylinder. The expanding vapor 
of the working fluid raises the right-hand piston, 
thus forcing working fluid to flow to the scientific 
instruments. 
When the left-hand piston reaches the bottom of 
its stroke, fluid flow in the heating coil of the right 
cylinder ceases and the working fluid vapor in the 
right-hand cylinder begins to condense because of the 
constant removal of energy at the cylinder surfaces 
in contact with the heat sink; as a result, the right-
hand piston descends and hot heat exchange fluid 
is drawn through the heating coil of the left-hand 
cylinder, which leads to raising of the left-hand piston 
and forcing of heat exchange fluid to the scientific 
instruments. The cylinders operate in a manner in 
which the pump is a mechanical analog of an astable 
electronic flip-flop; in the diagram, mechanical check 
valves are denoted by the electronic diode symbol. 
The coil springs indicated in the diagram are merely 
symbolic representations of forces which are required 
to drive the pistons during the course of pump opera-
tion; however, springs may be utilized to adjust the 
operating temperature of the pump.
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91108 
Reference: TSP 72-10728 
Patent status: 
This invention is owned by NASA, and a patent 
application has been filed. Inquiries concerning non-
exclusive or exclusive license for its commercial de-
velopment should be addressed to: 
NASA Patent Counsel 
Mail Code 1 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Eric E. Sabelman of 
Caltech/JPL
under contract to 
NASA Pasadena Office
(NPO-1 1417)
E1 
. 
F] 
B72-10723	 Category 06


Thermal-powered reciprocating pump

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server