received by the International Bureau on 24 July 2016(24.07.2016)

I claim-

1. An annular-shaped heat exchanger with finned-tubes for exchanging heat with fluid flow, where the said heat exchanger comprises of:

a. an annulus formed by two cylinders which are hollow, tapered and co -axial, where the said annulus is maintained by multiple supports;

b. multiple zigzag arrangement of the finned-tubes passing through the said annulus and positioned along the length-wise direction of the said annulus, where the said multiple zigzag arrangement of the finned-tubes is made by installing multiple finned-tubes along the length-wise direction of the said annulus and the multiple finned-tubes pass through the annular region with their axis oriented in the radial direction, the finned-tubes closest to each end of the annulus have one end open, and beginning from one end of the said annulus, using bent tubes to connect the ends of the said finned-tubes with the ends of the adjacent finned-tubes along the length-wise direction of the said annulus, thereby making a continuous zigzag-shaped conduit between the open ends of the finned-tubes closest to the two ends of the annulus; c. two circular shaped tubes, each with a head tube and multiple tubular ports, where the said multiple tubular ports on each of the circular shaped tubes are equal in number to the number of finned-tubes closest to each end of the annulus and the said multiple tubular ports on each of the circular shaped tubes are connected to the finned-tubes closest to each end of the annulus, and the said head tube on each of the circular shaped tubes makes a continuous conduit between the head tubes on the two circular shaped tubes.

2. An annular-shaped heat exchanger with finned-tubes of claim 1, used in a closed cycle system, where the closed cycle system comprises of:

18 a. the said annular-shaped heat exchanger with finned-tubes, which absorbs the thermal energy from a hot fluid flowing through a conduit, the said hot fluid flows through the annulus and over the finned-tubes of the said annular-shaped heat exchanger with finned-tubes, said annular-shaped heat exchanger with finned-tubes contains a working fluid inside its tubes, said annular- shaped heat exchanger with finned-tubes absorbs the thermal energy from the said hot fluid flow to convert the said working fluid into vapor.

b. a turbo-expander, which receives the vapor of the said working fluid from the said annular-shaped heat exchanger with finned-tubes, the vapor of the said working fluid drives the said turbo- expander, and the said turbo-expander is connected to a device utilizing mechanical energy;

c. a condenser, which receives the said working fluid from the said turbo-expander and condenses the said working fluid; and

d. a pump, which receives the said working fluid from the said condenser and pumps the said working fluid to the said annular-shaped heat exchanger with finned-tubes; where the said working fluid from the said pump is received at a head tube of the said annular-shaped heat exchanger with finned-tubes, and the other head tube of the said annular-shaped heat exchanger with finned-tubes transfers the said working fluid to the said turbo-expander.

3. The system of claim 2, where the working fluid is an organic fluid.

4. A thermal energy recuperating system for an aircraft gas turbine engine without an exhaust nozzle to recover the thermal energy from the exhaust gas flowing through the exhaust system of the said engine, where the thermal energy recuperating

19 system is a closed cycle system comprising of:

a. an annular- shaped heat exchanger with tubes, installed in the exhaust system, wherein the said annular- shaped heat exchanger with tubes comprises of: an annulus formed by two cylinders which are hollow, tapered and co -axial, where the said annulus is maintained by multiple supports; multiple zigzag arrangement of tubes passing through the said annulus and positioned along the length-wise direction of the said annulus, where the said multiple zigzag arrangement of tubes is made by installing multiple tubes along the lengthwise direction of the said annulus and the multiple tubes pass through the annular region with their axis oriented in the radial direction, the tubes closest to each end of the annulus have one end open, and beginning from one end of the said annulus, using bent tubes to connect the ends of the said tubes with the ends of the adjacent tubes along the length-wise direction of the said annulus, thereby making a continuous zigzag-shaped conduit between the open ends of the tubes closest to the two ends of the annulus; two circular shaped tubes, each with a head tube and multiple tubular ports, where the said multiple tubular ports on each of the circular shaped tubes are equal in number to the number of tubes closest to each end of the annulus and said multiple tubular ports on each of the circular shaped tubes are connected to the tubes closest to each end of the annulus, and the said head tube on each of the circular shaped tubes makes a continuous conduit between the head tubes on the two circular shaped tubes, said annular- shaped heat exchanger with tubes contains a working fluid inside its tubes, the exhaust gas passes through the annulus and over the tubes of the said annular-shaped heat exchanger with tubes, said annular-shaped heat exchanger with tubes absorbs the thermal energy from the exhaust gas to convert the working fluid into vapor;

b. a turbo-expander, whi ch re c e i v e s the v ap or o f the s ai d worki n g

20 flu i d from the s ai d annular-shaped heat exchanger with tubes, and the vapor of the said working fluid drives the said turbo-expander;

c. a heating coiled-tube with fins, which is installed in the air inlet system of the said engine, receives the hot working fluid from the said turbo -expander, and is operated by a system comprising of electronic sensors with controllers during icing conditions to prevent ice ingestion by heating the inlet air of the said engine;

d. a condenser, which is operated by electronic sensors with controllers for necessary condensation of the said working fluid depending on the engine operating conditions, is connected to the said heating coiled-tube with fins during icing conditions where the flow of the said working fluid is from the heating coiled-tube with fins to the condenser, and connected directly to the said turbo-expander during non-icing conditions by a flow channel for condensing the said working fluid received from the said turbo-expander; and

e. a pump, which rec eive s the s aid working fluid from the conde n s er and pu mp s the s aid working flu id to the s aid annular-shaped heat exchanger with tubes, and is operated by electronic sensors with controllers for necessary pumping force depending on the engine operating conditions; where the said working fluid from the said pump is received at a head tube of the said annular-shaped heat exchanger with tubes, and the other head tube of the said annular-shaped heat exchanger with tubes transfers the said working fluid to the said turbo-expander.

The system of claim 4, where the annular-shaped heat exchanger with tubes, has tubes with fins.

The system of claim 4, where the working fluid is a refrigerant.

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7. The system of claim 4, where the working fluid is a siloxane.

8. The system of claim 4, where the turbo-expander is operatively connected to an electric generator.

9. The system of claim 4, where the turbo-expander is operatively in s talle d on a shaft.

10. The system of claim 4, where the turbo-expander is operatively connected to a turbo-machine.

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