A temperature adjustable spray collector

Abstract

This invention discloses a temperature-adjustable spray-type solar collector, belonging to the field of solar thermal utilization technology. Addressing the problems of existing solar collectors' efficiency being greatly affected by weather, unadjustable temperature, and large working fluid consumption, this invention includes a collector shell, a transparent cover, a Fresnel lens, a water coil, an atomizer, a nanofluid storage tank, a temperature sensor, and a controller. The transparent cover is located at the top of the shell, with a corrugated bottom coated with a hydrophobic coating; the Fresnel lens is positioned above the cover for focusing sunlight; the atomizer is connected to the storage tank, atomizing and spraying the nanofluid into the shell; the water coil is located inside the shell; the temperature sensor is located at the inlet and outlet of the water coil; the controller is connected to the temperature sensor and the atomizer, adjusting the spray volume according to the water temperature difference. When sunlight is insufficient, the spray volume is reduced to maintain the outlet water temperature; when sunlight is sufficient, the spray volume is increased to utilize solar energy. This invention features high efficiency, low working fluid consumption, and intelligent temperature control, and can be used for solar water heating.

Description

Technical Field

[0001] This invention relates to the field of solar thermal utilization technology, and specifically to a temperature-adjustable spray collector. Background Technology

[0002] Solar energy, as a new type of renewable energy, has become an important choice for achieving carbon neutrality due to its abundant reserves, stable and long-term availability, cleanliness, and low cost. The core component of solar thermal utilization technology is the solar collector. Currently, solar collectors are mainly divided into two types: indirect collectors and direct-suction collectors.

[0003] When an indirect solar collector (including flat plate collectors and evacuated tube collectors) is working, solar radiation energy is first absorbed by the absorption coating and converted into heat energy, and then the heat energy is transferred to the working medium through heat conduction and convection. However, traditional indirect collectors have the following defects: (1) The heat collection medium uses traditional phase change materials, which need to be covered to ensure uniform heating, and the amount of heat collection medium used is large; (2) The heat collection medium comes into contact with the cover plate, causing the cover plate to heat up and the surface heat loss is high; although evacuated tubes can reduce heat loss, they are expensive; (3) Traditional concentrating technologies are complex and the concentrating effect is inconsistent; (4) The heat collection efficiency is greatly affected by the weather, and it is difficult to reach the set temperature when there is insufficient sunlight.

[0004] Direct-suction solar collectors use nanofluids as the direct heat transfer medium. Nanofluids are both light-absorbing materials and heat transfer fluids, and their photothermal conversion performance is superior to that of traditional working fluids. However, nanofluids are prone to sedimentation, which is a disadvantage in terms of stability.

[0005] Therefore, there is an urgent need for a solar collector that can overcome the above-mentioned defects, has high heat collection efficiency, and allows for flexible temperature control. Summary of the Invention

[0006] In view of the shortcomings of existing solar collectors, such as large amount of heat-collecting working fluid, high surface heat loss, unsatisfactory light-concentrating effect, and heat collection efficiency greatly affected by weather and inflexible temperature control, this invention provides a spray-type solar collector with adjustable temperature.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An adjustable temperature spray solar collector includes:

[0009] Solar collector shell;

[0010] A transparent cover plate is disposed on the top of the collector shell, and the bottom of the transparent cover plate is corrugated and coated with a hydrophobic coating;

[0011] A Fresnel lens, positioned above the transparent cover, is used to focus sunlight.

[0012] A water coil is installed inside the collector shell and is used for heat exchange with the heat collection medium;

[0013] Nanofluid storage tank, used to store nanofluids;

[0014] Atomizer, connected to the nanofluid storage tank, is used to atomize the nanofluid and spray it into the interior of the solar collector housing;

[0015] Temperature sensors are respectively installed at the inlet and outlet of the water coil to monitor the inlet and outlet water temperatures in real time.

[0016] The controller, connected to the temperature sensor and the atomizer, is used to adjust the spray volume of the atomizer according to the temperature difference between the inlet and the outlet, so as to adjust the heat collection temperature of the collector housing, thereby making the temperature of the outlet reach the set temperature.

[0017] Furthermore, the controller is configured to: reduce the spray volume of the atomizer when the outlet temperature is lower than the set temperature, so that the nanofluid heats up and releases enough heat in a short time to ensure that the outlet temperature meets the standard; and increase the spray volume of the atomizer when the outlet temperature is higher than the set temperature to make full use of solar energy.

[0018] Furthermore, the controller is configured to: calculate the heat collection capacity of the solar collector, compare the theoretical temperature rise corresponding to the calculated heat collection capacity with the measured temperature rise, determine the illumination conditions, and then adjust the spray volume of the atomizer.

[0019] Furthermore, the controller is configured to adjust the heat collection temperature by adjusting the spray volume of the atomizer when the light conditions change, so as to ensure a balance between heat supply and demand.

[0020] Furthermore, the nanofluid is a SiC-water nanofluid, which can improve the heat collection efficiency by about 20% under the same heat collector conditions.

[0021] Furthermore, the corrugated bottom of the transparent cover has a serrated slope, which prevents droplets from accumulating on the cover surface and reduces heat loss caused by the cover heating up.

[0022] Furthermore, the collector shell does not have a vacuum tube inside, simplifying the structure and reducing costs. Furthermore, the atomizer is an ultrasonic atomizer with adjustable spray volume, producing uniform and small-sized droplet particles.

[0023] Furthermore, it also includes a recovery pipeline connecting the bottom of the solar collector shell to the nanofluid storage tank for collecting the condensed nanofluid and recycling it.

[0024] Furthermore, the controller is also connected to the inlet valve and outlet valve respectively installed at the inlet and outlet of the water coil, for adjusting the water flow rate according to the outlet temperature or the temperature difference between the inlet and outlet.

[0025] Furthermore, the nanofluid is an aqueous dispersion of carbon nanotubes.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The innovative temperature control function monitors the inlet and outlet water temperatures in real time through temperature sensors. The controller adjusts the spray volume according to the temperature difference. When there is insufficient sunlight, the spray volume is reduced to ensure that the outlet water temperature meets the standard. When there is sufficient sunlight, the spray volume is increased to make full use of solar energy, thus realizing flexible control of the heat collection temperature and supply and demand balance.

[0028] Significantly improves solar energy collection efficiency: The Fresnel lens is used to concentrate light, which greatly increases the solar energy absorption rate; the SiC-water nanofluid spray heat collection method can improve the solar energy collection efficiency by about 20% under the same conditions; according to calculations, the efficiency of the new solar collector is about 59.6%, which is significantly improved compared to the 44.2% of the traditional solar collector.

[0029] Significantly reduces the amount of heat collection medium: The spray heat collection method replaces the traditional full-tube heat collection method, which can achieve a faster temperature rise with only a small amount of spray, thus greatly reducing the amount of heat collection medium used.

[0030] Effectively reduces heat loss: The bottom of the cover plate is corrugated and coated with a hydrophobic coating, which prevents droplets from accumulating on the surface of the cover plate and reduces heat loss caused by the heating of the cover plate; the nanofluid spray has a low density and less contact with the top plate, further reducing surface heat loss.

[0031] Solving the problem of nanofluid sedimentation: The nanofluid is atomized and sprayed into the collector using a spray method, which avoids the problem of easy sedimentation of nanofluid in traditional direct-suction collectors.

[0032] Simplified structure and reduced cost: The elimination of vacuum tubes simplifies the collector structure and reduces manufacturing and maintenance costs.

[0033] Significant energy-saving and environmental protection benefits: Taking Nanjing as an example, at 2780m... 2 Based on the collected heat area, the annual electricity saving is approximately 450,900 kWh, and the annual CO2 emission reduction is approximately 449.51 tons. Attached Figure Description

[0034] Figure 1 A schematic diagram of the overall structure of a solar collector heating system;

[0035] Figure 2 This is a schematic diagram of the solar collector model structure;

[0036] Figure 3This is a schematic diagram illustrating the light-gathering principle of a Fresnel lens.

[0037] Figure 4 This is a schematic diagram of the thermal process of a solar collector.

[0038] Figure 5 Bar chart showing the temperature rise of nanofluid spray under different illumination conditions. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] Example 1: Solar Collector Structure

[0041] like Figure 1 and Figure 2 As shown, the temperature-adjustable spray-type solar collector of this embodiment includes a collector housing, a transparent cover, a Fresnel lens, a water coil, an atomizer, a nanofluid storage tank, a temperature sensor, and a controller. Figure 3 As shown, the Fresnel lens focuses sunlight at a point, and the collector housing is located near the focal point of the Fresnel lens.

[0042] The collector shell has a rectangular structure, measuring 25cm in length, 17cm in width, and 13cm in height. A transparent cover plate is located on the top of the shell, with a corrugated bottom (a steep slope, almost sawtooth-like) and coated with a hydrophobic coating to prevent mist droplets from accumulating on the cover surface. A Fresnel lens, measuring 50mm × 50mm, with a theoretical focal length of 620mm (experimentally determined to be approximately 600mm), is positioned above the transparent cover plate. In this embodiment, no vacuum tube is installed inside the collector shell, simplifying the structure and reducing costs.

[0043] The water coil is made of copper tubing with an outer diameter of 6mm and is installed inside the collector housing. The atomizer is a small, household-grade atomizer with adjustable spray volume (e.g., an ultrasonic atomizer), with the spray volume adjustable via a knob, and is connected to the nanofluid storage tank. The nanofluid is either JCWCNDM-2 type carbon nanotube aqueous dispersion (small-diameter multi-walled carbon nanotube aqueous dispersion, slurry solid content 3.2wt%, carbon nanotube solid content 2wt%), or SiC-water nanofluid.

[0044] Temperature sensors (thermocouple temperature sensors) are installed at the inlet and outlet of the water coil to monitor the inlet and outlet water temperatures in real time. A controller is connected to the temperature sensors and the atomizer to adjust the atomizer's spray volume based on the inlet and outlet temperature difference, thereby regulating the collector temperature of the collector shell and ensuring the outlet temperature reaches the set temperature. The controller is also connected to inlet and outlet valves respectively installed at the inlet and outlet of the water coil to adjust the water flow rate based on the outlet temperature or the temperature difference between the inlet and outlet.

[0045] The bottom of the collector shell is equipped with a recovery pipeline that connects to a nanofluid storage tank to collect the condensed nanofluid and recycle it.

[0046] Example 2: Working Process and Temperature Control Principle

[0047] like Figure 4 As shown, when the solar collector is working, the collector model is placed near the focal point of the Fresnel lens under sunlight (or under a xenon lamp simulated light source). The atomizer is turned on, and the nanofluid solution enters and is atomized into small, uniform droplets that enter the collector. The nanofluid spray absorbs the solar energy concentrated by the Fresnel lens and rapidly heats up. Water is then introduced into the copper tube, where the droplets deposit and adhere to the surface of the tube, exchanging heat thoroughly with the fluid inside and condensing into liquid droplets. The condensed nanofluid is discharged from the bottom of the collector and recycled back into the atomizer via a recovery pipeline. The water in the tube, after absorbing heat, reaches the set temperature and is then discharged for use by home users.

[0048] The temperature control principle is as follows: Assume a room temperature of 18℃, an inlet water temperature of 60℃, and an outlet water temperature of 70℃, with a temperature difference of approximately 10℃ between the inlet and outlet. When the outlet temperature is below 70℃, it indicates low light intensity and poor weather conditions, preventing the collector from reaching the set temperature. In this case, the controller reduces the atomizer's spray volume and appropriately decreases the water flow rate, allowing the nanofluid to gain sufficient temperature rise and release heat in a short time, ensuring the outlet water temperature reaches 70℃. When the outlet temperature is above 70℃, it indicates good light intensity and sunny weather, resulting in good heat collection. In this case, the controller increases the atomizer's spray volume and appropriately increases the water flow rate, enabling the collector to utilize more solar energy for heating.

[0049] The controller is further configured to: calculate the heat collection capacity of the solar collector based on the temperature difference between the inlet and outlet, compare it with the theoretical temperature rise, determine the illumination conditions, and then adjust the spray volume of the atomizer. Changes in illumination intensity lead to changes in the Fresnel lens's heat collection effect, resulting in changes in the solar collector's heat collection capacity, the heat absorption of the nanofluid spray, and the amount of replenished nanofluid condensate. The controller adjusts the spray volume by adjusting the atomizer knob, thereby increasing or decreasing the nanofluid temperature rise and releasing an appropriate amount of heat in a short time, ensuring the hot water supply temperature while ensuring stable system operation. The controller is also configured to: adjust the solar collector temperature by adjusting the spray volume of the atomizer when illumination conditions change, to ensure a balance between heat supply and demand.

[0050] Example 3: Controller

[0051] In this embodiment, the controller is implemented using a microcontroller (such as the STM32 series). The temperature sensor is a thermocouple, and its output signal is converted into a digital signal by an A / D conversion module before being input to the microcontroller. The microcontroller has a preset temperature T0 (e.g., 70°C) and stores the control program.

[0052] The control procedure includes the following steps:

[0053] (1) Collect the inlet temperature t1 and outlet temperature t2 of the water coil;

[0054] (2) Calculate the temperature difference Δt = t2 - t1, and determine whether the outlet temperature t2 is lower than the set temperature T0;

[0055] (3) When t2 < T0, the microcontroller outputs a control signal to reduce the spray volume of the atomizer; when t2 > T0, the microcontroller outputs a control signal to increase the spray volume of the atomizer.

[0056] (4) Further, the microcontroller calculates the heat collection capacity Q' of the solar collector based on the temperature difference Δt and compares it with the theoretical temperature rise: if the theoretical temperature rise is less than the actual temperature rise, it indicates that the light conditions are poor and the spray volume should be reduced; if the theoretical temperature rise is greater than the actual temperature rise, it indicates that the light conditions are strong and the spray volume should be increased.

[0057] (5) The microcontroller controls the opening of the atomizer's adjustment knob or solenoid valve by outputting a PWM signal or an analog voltage signal, thereby changing the spray volume.

[0058] The controller can also be connected to the inlet valve and the outlet valve to adjust the water flow rate according to the outlet temperature or the temperature difference between the inlet and outlet.

[0059] Example 4: Experimental Verification

[0060] A heat collection simulation experiment was conducted using a xenon lamp simulator, with heat collection monitoring performed at currents of 10A, 15A, and 20A. Nanofluid was introduced, and the spray temperature inside the collector was monitored using thermocouples. The temperature rise per minute was recorded to evaluate the heat collection efficiency. Experimental results show that the temperature increase varies under different current conditions, but the overall temperature rise is relatively rapid, demonstrating good collector performance. Figure 5 As shown, the temperature rise of the xenon lamp under 10A, 15A, and 20A conditions is approximately 1.1, 1.9, and 2.7, respectively, while the temperature rise under sunlight is approximately 2.2.

[0061] On a sunny afternoon at 4 PM, the solar collector model was placed under a Fresnel lens and connected to a water body. The spray temperature, inlet and outlet water temperatures, and concentrated illuminance inside the collector were monitored. The results showed that the spray temperature rose rapidly in a short time after focusing, and then remained at around 50°C for a period of time (continuous heat exchange). The return water temperature gradually increased with the heat collection time, rising by about 15°C within 5 minutes, indicating that the solar collector had a good rapid heating function.

[0062] After the nanofluid concentration approximately stabilizes, all the heat collected by the nanofluid eventually enters the water coil (ignoring heat dissipation). The heat absorbed by the water coil is calculated using the formula Q = c × V × ρ × (t2 - t1). Where c is the specific heat capacity of water; V is the volume of water flowing through the water coil; ρ is the density of water; t2 is the outlet temperature of the water coil; and t1 is the inlet temperature of the water coil. Comparing the theoretical temperature rise with the actual temperature rise measured by thermocouples: if the theoretical temperature rise is less than the actual temperature rise, it indicates poor lighting conditions, and the fog volume should be reduced to reach the set temperature; if the theoretical temperature rise is greater than the actual temperature rise, it indicates strong lighting conditions, and the fog volume should be increased to better utilize solar energy. Combined with illuminance meter data, the collector efficiency can be estimated.

[0063] Calculations show that the heat collection efficiency of traditional solar collectors is approximately 44.2%, while the efficiency of the solar collector of this invention is approximately 59.6%. Taking Nanjing as an example, the average sunshine duration is approximately 13.33 hours, and at a depth of 2780m... 2 Based on the collector area, the total annual heat collection is approximately 6.49 × 10⁻⁶. 9 KJ, annual electricity savings of approximately 450,900 kWh, and annual reduction of CO2 emissions of approximately 449.51 tons.

Claims

1. A temperature-adjustable spray-type solar collector, characterized in that, include: Solar collector shell; A transparent cover plate is disposed on the top of the collector shell, and the bottom of the transparent cover plate is corrugated and coated with a hydrophobic coating; A Fresnel lens, positioned above the transparent cover, is used to focus sunlight. A water coil is installed inside the collector shell and is used for heat exchange with the heat collection medium; Nanofluid storage tank, used to store nanofluids; Atomizer, connected to the nanofluid storage tank, is used to atomize the nanofluid and spray it into the interior of the solar collector housing; Temperature sensors are respectively installed at the inlet and outlet of the water coil to monitor the inlet and outlet water temperatures in real time. The controller, connected to the temperature sensor and the atomizer, is used to adjust the spray volume of the atomizer according to the temperature difference between the inlet and the outlet, so as to adjust the heat collection temperature of the collector housing, thereby making the temperature of the outlet reach the set temperature.

2. The adjustable temperature spray collector according to claim 1, characterized in that, The controller is configured to: When the outlet temperature is lower than the set temperature, the spray volume of the atomizer is reduced so that the nanofluid heats up and releases enough heat to ensure that the outlet temperature meets the standard. When the outlet temperature is higher than the set temperature, the spray volume of the atomizer is increased to make full use of solar energy.

3. The adjustable temperature spray collector according to claim 1, characterized in that, The controller is configured to: calculate the heat collection capacity of the solar collector, compare the theoretical temperature rise corresponding to the calculated heat collection capacity with the measured temperature rise, determine the illumination conditions, and then adjust the spray volume of the atomizer.

4. The adjustable temperature spray collector according to claim 1, characterized in that, The controller is configured to adjust the heat collection temperature by adjusting the spray volume of the atomizer when the light conditions change, so as to ensure a balance between heat supply and demand.

5. The adjustable temperature spray collector according to claim 1, characterized in that, The nanofluid is a SiC-water nanofluid or a carbon nanotube aqueous dispersion.

6. The adjustable temperature spray collector according to claim 1, characterized in that, It also includes a recovery pipeline for collecting the condensed nanofluid, the recovery pipeline connecting the bottom of the collector housing to the nanofluid storage tank.

7. The temperature-adjustable spray collector according to claim 1, characterized in that, The corrugated bottom of the transparent cover has a serrated slope.

8. The temperature-adjustable spray collector according to claim 1, characterized in that, The atomizer is an ultrasonic atomizer with adjustable spray volume.

9. The adjustable temperature spray collector according to claim 1, characterized in that, The controller is also connected to the inlet valve and outlet valve respectively installed at the inlet and outlet of the water coil, and is used to adjust the water flow rate according to the outlet temperature or the temperature difference between the inlet and outlet.

Images